Work, Energy and Power 11th Science Lesson
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Question 1 of 75
1. Question
Assertion (A): Physics defines work as the work done by a force when applied on a body.
Reasoning(R): Work refers to both physical and mental work.Correct
The term work is used in diverse contexts in daily life. It refers to both physical as well as mental work. In fact, any activity can generally be called as work. But in Physics, the term work is treated as a physical quantity with a precise definition. Work is said to be done by the force when the force applied on a body displaces it.
Incorrect
The term work is used in diverse contexts in daily life. It refers to both physical as well as mental work. In fact, any activity can generally be called as work. But in Physics, the term work is treated as a physical quantity with a precise definition. Work is said to be done by the force when the force applied on a body displaces it.

Question 2 of 75
2. Question
Choose the Incorrect statements.
i) Energy is defined as the ability to do work.
ii) Work and energy are not same in definition and dimensions.
iii) Energy exists in various forms as Electrical, Thermal and Mechanical and so on.Correct
To do work, energy is required. In simple words, energy is defined as the ability to do work. Hence, work and energy are equivalents and have same dimension. Energy, in Physics exists in different forms such as mechanical, electrical, thermal, and nuclear and so on.
Incorrect
To do work, energy is required. In simple words, energy is defined as the ability to do work. Hence, work and energy are equivalents and have same dimension. Energy, in Physics exists in different forms such as mechanical, electrical, thermal, and nuclear and so on.

Question 3 of 75
3. Question
Assertion (A): Work is a scalar quantity which has only magnitude and no direction.
Reasoning(R): The scalar product of two vectors is a scalar.Correct
The product F. dr is a scalar product (or dot product). The scalar product of two vectors is a scalar. Thus, work done is a scalar quantity. It has only magnitude and no direction
Incorrect
The product F. dr is a scalar product (or dot product). The scalar product of two vectors is a scalar. Thus, work done is a scalar quantity. It has only magnitude and no direction

Question 4 of 75
4. Question
What is the dimensional formula of work done on a object?
 a) MT^{1}
 b) ML^{2}T
 c) ML^{2}T^{2}
 d) ML^{2}T^{2}
Correct
In SI system, unit of work done is N m (or) joule (J). Its dimensional formula is [ML^{2}T^{2}].
Incorrect
In SI system, unit of work done is N m (or) joule (J). Its dimensional formula is [ML^{2}T^{2}].

Question 5 of 75
5. Question
The angle value of the work is calculated between the force and ____.
Correct
W= F dr cosθ which can be realized using the below diagram.
Incorrect
W= F dr cosθ which can be realized using the below diagram.

Question 6 of 75
6. Question
Which of this value is not related to the work done on an object?
Correct
The work done by the force depends on the force (F), displacement (dr) and the angle (θ) between them.
Incorrect
The work done by the force depends on the force (F), displacement (dr) and the angle (θ) between them.

Question 7 of 75
7. Question
In which of the following cases the work done may not be zero?
Correct
Work done is zero in the following cases. When the force is zero (F = 0). For example, a body moving on a horizontal smooth frictionless surface will continue to do so as no force (not even friction) is acting along the plane. (This is an ideal situation.). When the displacement is zero (dr = 0). For example, when force is applied on a rigid wall it does not produce any displacement.
Incorrect
Work done is zero in the following cases. When the force is zero (F = 0). For example, a body moving on a horizontal smooth frictionless surface will continue to do so as no force (not even friction) is acting along the plane. (This is an ideal situation.). When the displacement is zero (dr = 0). For example, when force is applied on a rigid wall it does not produce any displacement.

Question 8 of 75
8. Question
Which of this force does no work on a body if it moves in a horizontal direction?
Correct
When the force and displacement are perpendicular (θ = 90°) to each other. When a body moves on a horizontal direction, the gravitational force (mg) does no work on the body, since it acts at right angles to the displacement. In circular motion the centripetal force does not do work on the object moving on a circle as it is always perpendicular to the displacement.
Incorrect
When the force and displacement are perpendicular (θ = 90°) to each other. When a body moves on a horizontal direction, the gravitational force (mg) does no work on the body, since it acts at right angles to the displacement. In circular motion the centripetal force does not do work on the object moving on a circle as it is always perpendicular to the displacement.

Question 9 of 75
9. Question
Choose the incorrect statements.
 i) The value of displacement by a given force to the body decides the work done.
 ii) The goal keeper catching a ball towards him is an example of negative work.
Correct
For a given force (F) and displacement (dr) the angle (θ) between them decides the value of work done. There are many examples for the negative work done by a force. In a football game, the goalkeeper catches the ball coming towards him by applying a force such that the force is applied in a direction opposite to that of the motion of the ball till it comes to rest in his hands. During the time of applying the force, he does a negative work on the ball.
Incorrect
For a given force (F) and displacement (dr) the angle (θ) between them decides the value of work done. There are many examples for the negative work done by a force. In a football game, the goalkeeper catches the ball coming towards him by applying a force such that the force is applied in a direction opposite to that of the motion of the ball till it comes to rest in his hands. During the time of applying the force, he does a negative work on the ball.

Question 10 of 75
10. Question
A cart is pulled with a force of 50 N to produce a displacement of 25 m. If the angle between the force and displacement is 45°, find the work done by the force.
Correct
Force, F = 50 N , Displacement, dr = 25 m, Angle between F and dr, θ = 45°,
Work done, W= F dr cosθ
W= 50 ×25 × cos45° = 50 ×25 × 0.7071
W= 883.86 JIncorrect
Force, F = 50 N , Displacement, dr = 25 m, Angle between F and dr, θ = 45°,
Work done, W= F dr cosθ
W= 50 ×25 × cos45° = 50 ×25 × 0.7071
W= 883.86 J 
Question 11 of 75
11. Question
Match.
 Angle Work
 180° i) Positive
 0< θ < 90° ii) Zero
 0° iii) Maximum negative
 90° iv) Maximum positive
Correct
Incorrect

Question 12 of 75
12. Question
What is the value of angle between the force and displacement if an object is thrown upwards from the ground?
Correct
When the object goes up the displacement points in the upward direction whereas the gravitational force acting on the object points in downward direction. Therefore the angle between gravitational force and displacement of the object is 180°.
Incorrect
When the object goes up the displacement points in the upward direction whereas the gravitational force acting on the object points in downward direction. Therefore the angle between gravitational force and displacement of the object is 180°.

Question 13 of 75
13. Question
Calculate the work done by the gravity when a weight lifter lifts a mass of 250 kg with a force 5000 N to the height of 5 m.
Correct
When the weight lifter lifts the mass, the gravity acts downwards which means that the force and displacement are in opposite direction. Therefore, the angle between them 180° W gravity = F h mg hg cos 180°= – 12.5 k J
Incorrect
When the weight lifter lifts the mass, the gravity acts downwards which means that the force and displacement are in opposite direction. Therefore, the angle between them 180° W gravity = F h mg hg cos 180°= – 12.5 k J

Question 14 of 75
14. Question
State the component of variable force F acting on a body to do a small work dW?
Correct
When the component of a variable force F acts on a body, the small work done (dW) by the force in producing a small displacement dr is given by the relation dW ‑F cosdr [F cos q is the component of the variable force F]
Incorrect
When the component of a variable force F acts on a body, the small work done (dW) by the force in producing a small displacement dr is given by the relation dW ‑F cosdr [F cos q is the component of the variable force F]

Question 15 of 75
15. Question
Which of the following is not true regarding energy and work?
Correct
Energy is defined as the capacity to do work. In other words, work done is the manifestation of energy. That is why work and energy have the same dimension (ML ^{2}T^{2})
Incorrect
Energy is defined as the capacity to do work. In other words, work done is the manifestation of energy. That is why work and energy have the same dimension (ML ^{2}T^{2})

Question 16 of 75
16. Question
Which of the following statements are not true?
Correct
The important aspect of energy is that for an isolated system, the sum of all forms of energy i.e., the total energy remains the same in any process irrespective of whatever internal changes may take place. This means that the energy disappearing in one form reappears in another form. This is known as the law of conservation of energy.
Incorrect
The important aspect of energy is that for an isolated system, the sum of all forms of energy i.e., the total energy remains the same in any process irrespective of whatever internal changes may take place. This means that the energy disappearing in one form reappears in another form. This is known as the law of conservation of energy.

Question 17 of 75
17. Question
Choose the Incorrect statements.
 i) The Frictional forces are classified into two types as Kinetic and Potential energy.
 ii) Kinetic energy is the energy possessed by a body due to its motion.
 iii) The energy possessed by the body by virtue of its position is known as potential energy.
Correct
In a broader sense, mechanical energy is classified into two types, Kinetic energy and Potential energy. The energy possessed by a body due to its motion is called kinetic energy. The energy possessed by the body by virtue of its position is called potential energy.
Incorrect
In a broader sense, mechanical energy is classified into two types, Kinetic energy and Potential energy. The energy possessed by a body due to its motion is called kinetic energy. The energy possessed by the body by virtue of its position is called potential energy.

Question 18 of 75
18. Question
What is the SI unit of the energy?
Correct
The SI unit of energy is the same as that of work done i.e., N m (or) joule (J). The dimension of energy is also the same as that of work done. It is given by [ML2T2].
Incorrect
The SI unit of energy is the same as that of work done i.e., N m (or) joule (J). The dimension of energy is also the same as that of work done. It is given by [ML2T2].

Question 19 of 75
19. Question
. Match
 1 electron volt i) 4.186 J
 1 erg ii) 1.6 x 10^{19}J
 1 kilowatt hour iii) 10^{7}J
 1 calorie iv) 3.6 x 10^{6}J
Correct
SI equivalent of other units of energy
Incorrect
SI equivalent of other units of energy

Question 20 of 75
20. Question
Assertion (A): Kinetic energy is the energy possessed by a body by virtue of its motion.
Reasoning(R): All moving objects have kinetic energy.
Correct
Kinetic energy is the energy possessed by a body by virtue of its motion. All moving objects have kinetic energy. A body that is in motion has the ability to do work. For example a hammer kept at rest on a nail does not push the nail into the wood. Whereas the same hammer when it strikes the nail, draws the nail into the wood.
Incorrect
Kinetic energy is the energy possessed by a body by virtue of its motion. All moving objects have kinetic energy. A body that is in motion has the ability to do work. For example a hammer kept at rest on a nail does not push the nail into the wood. Whereas the same hammer when it strikes the nail, draws the nail into the wood.

Question 21 of 75
21. Question
Which of the values are dependent on the Kinetic energy of a body?
Correct
Kinetic energy is measured by the amount of work that the body can perform before it comes to rest. The amount of work done by a moving body depends both on the mass of the body and the magnitude of its velocity. A body which is not in motion does not have kinetic energy.
Incorrect
Kinetic energy is measured by the amount of work that the body can perform before it comes to rest. The amount of work done by a moving body depends both on the mass of the body and the magnitude of its velocity. A body which is not in motion does not have kinetic energy.

Question 22 of 75
22. Question
What is the expression for a constant force?
Correct
The constant force is given by the equation, F =ma
Incorrect
The constant force is given by the equation, F =ma

Question 23 of 75
23. Question
State the expression for the kinetic energy with mass m and velocity v.
 a) KE = ½ mv^{2}
 b) KE = mv^{2}
 c) KE = ma
 d) KE = ¼ mv
Correct
The expression for kinetic energy: The kinetic energy of the body of mass (m) moving with velocity (v).
Incorrect
The expression for kinetic energy: The kinetic energy of the body of mass (m) moving with velocity (v).

Question 24 of 75
24. Question
Choose the correct statements.
 i) The value of the Kinetic energy is always negative.
 ii) The Kinetic energy is changed by the work done on the body
Correct
Kinetic energy of the body is always positive.
The expression on the right hand side (RHS) of equation is the change in kinetic energy (ΔKE) of the body. This implies that the work done by the force on the body changes the kinetic energy of the body. This is called workkinetic energy theorem.
Incorrect
Kinetic energy of the body is always positive.
The expression on the right hand side (RHS) of equation is the change in kinetic energy (ΔKE) of the body. This implies that the work done by the force on the body changes the kinetic energy of the body. This is called workkinetic energy theorem.

Question 25 of 75
25. Question
Which of these are implied from the workkinetic energy theorem?
Correct
The workkinetic energy theorem implies the following. If the work done by the force on the body is positive then its kinetic energy increases. If the work done by the force on the body is negative then its kinetic energy decreases. If there is no work done by the force on the body then there is no change in its kinetic energy, which means that the body has moved at constant speed provided its mass remains constant.
Incorrect
The workkinetic energy theorem implies the following. If the work done by the force on the body is positive then its kinetic energy increases. If the work done by the force on the body is negative then its kinetic energy decreases. If there is no work done by the force on the body then there is no change in its kinetic energy, which means that the body has moved at constant speed provided its mass remains constant.

Question 26 of 75
26. Question
Assertion (A): The magnitude of the momentum is only calculated from the kinetic energy and the mass of the object.
Reasoning(R): The Kinetic energy and the mass are the scalars
Correct
If kinetic energy and mass are given, only the magnitude of the momentum can be calculated but not the direction of momentum. It is because the kinetic energy and mass are scalars.
Incorrect
If kinetic energy and mass are given, only the magnitude of the momentum can be calculated but not the direction of momentum. It is because the kinetic energy and mass are scalars.

Question 27 of 75
27. Question
Which of these factors is associated with the potential energy of a body?
Correct
The potential energy of a body is associated with its position and configuration with respect to its surroundings. This is because the various forces acting on the body also depends on position and configuration. “Potential energy of an object at a point P is defined as the amount of work done by an external force in moving the object at constant velocity from the point O (initial location) to the point P (final location). At initial point O potential energy can be taken as zero.
Incorrect
The potential energy of a body is associated with its position and configuration with respect to its surroundings. This is because the various forces acting on the body also depends on position and configuration. “Potential energy of an object at a point P is defined as the amount of work done by an external force in moving the object at constant velocity from the point O (initial location) to the point P (final location). At initial point O potential energy can be taken as zero.

Question 28 of 75
28. Question
Which of the following statement is not true regarding the workkinetic energy theorem?
Correct
The workkinetic energy theorem implies the following. If the work done by the force on the body is positive then its kinetic energy increases. If the work done by the force on the body is negative then its kinetic energy decreases. If there is no work done by the force on the body then there is no change in its kinetic energy, which means that the body has moved at constant speed provided its mass remains constant.
Incorrect
The workkinetic energy theorem implies the following. If the work done by the force on the body is positive then its kinetic energy increases. If the work done by the force on the body is negative then its kinetic energy decreases. If there is no work done by the force on the body then there is no change in its kinetic energy, which means that the body has moved at constant speed provided its mass remains constant.

Question 29 of 75
29. Question
Which of these is not a type of the potential energy?
Correct
We have various types of potential energies. Each type is associated with a particular force. For example, The energy possessed by the body due to gravitational force gives rise to gravitational potential energy. The energy due to spring force and other similar forces give rise to elastic potential energy. The energy due to electrostatic force on charges gives rise to electrostatic potential energy.
Incorrect
We have various types of potential energies. Each type is associated with a particular force. For example, The energy possessed by the body due to gravitational force gives rise to gravitational potential energy. The energy due to spring force and other similar forces give rise to elastic potential energy. The energy due to electrostatic force on charges gives rise to electrostatic potential energy.

Question 30 of 75
30. Question
Which of this value is constant in calculating the gravitational potential energy?
Correct
The gravitational potential energy (U) at some height h is equal to the amount of work required to take the object from ground to that height h with constant velocity.
Incorrect
The gravitational potential energy (U) at some height h is equal to the amount of work required to take the object from ground to that height h with constant velocity.

Question 31 of 75
31. Question
What is the value of the gravitational potential energy?
Correct
The gravitational potential energy (U) at some height h is equal to the amount of work required to take the object from the ground to that height h.
Incorrect
The gravitational potential energy (U) at some height h is equal to the amount of work required to take the object from the ground to that height h.

Question 32 of 75
32. Question
Assertion (A): Potential energy stored in an object is defined by the work done by the external positive force.
Reasoning(R): The external force transfers the energy to the object as potential energy.
Correct
The potential energy stored in the object is defined through work done by the external force which is positive. Physically this implies that the agency which is applying the external force is transferring the energy to the object which is then stored as potential energy. If the object is allowed to fall from a height h then the stored potential energy is converted into kinetic energy.
Incorrect
The potential energy stored in the object is defined through work done by the external force which is positive. Physically this implies that the agency which is applying the external force is transferring the energy to the object which is then stored as potential energy. If the object is allowed to fall from a height h then the stored potential energy is converted into kinetic energy.

Question 33 of 75
33. Question
How can an object move with zero acceleration (constant velocity) when the external force is acting on the object?
Correct
It is possible when there is another force which acts exactly opposite to the external applied force. They both cancel each other and the resulting net force becomes zero, hence the object moves with zero acceleration.
Incorrect
It is possible when there is another force which acts exactly opposite to the external applied force. They both cancel each other and the resulting net force becomes zero, hence the object moves with zero acceleration.

Question 34 of 75
34. Question
Which of this value is kept as a constant value when defining the potential energy?
Correct
If the object does not move at constant velocity, then it will have different velocities at the initial and final locations. According to work kinetic energy theorem, the external force will impart some extra kinetic energy. But we associate potential energy to the forces like gravitational force, spring force and Coulomb force. So the external agency should not impart any kinetic energy when the object is taken from initial to final location.
Incorrect
If the object does not move at constant velocity, then it will have different velocities at the initial and final locations. According to work kinetic energy theorem, the external force will impart some extra kinetic energy. But we associate potential energy to the forces like gravitational force, spring force and Coulomb force. So the external agency should not impart any kinetic energy when the object is taken from initial to final location.

Question 35 of 75
35. Question
Choose the Incorrect statements.
 i) A restoring force is developed in a spring when it is elongated.
 ii) The Kinetic energy possessed by a spring due to deforming force is termed as elastic potential energy.
 iii) The work done against the restoring force of a spring is stored as elastic potential energy.
Correct
When a spring is elongated, it develops a restoring force. The potential energy possessed by a spring due to a deforming force which stretches or compresses the spring is termed as elastic potential energy. The work done by the applied force against the restoring force of the spring is stored as the elastic potential energy in the spring.
Incorrect
When a spring is elongated, it develops a restoring force. The potential energy possessed by a spring due to a deforming force which stretches or compresses the spring is termed as elastic potential energy. The work done by the applied force against the restoring force of the spring is stored as the elastic potential energy in the spring.

Question 36 of 75
36. Question
What is the sign of the restoring force developed in a spring?
Correct
According Hooke’s law, the restoring force developed in the spring is
The negative sign in the above expression implies that the spring force is always opposite to that of displacement x and k is the force constant. Therefore applied force is F_{a} = +kx. The positive sign implies that the applied force is in the direction of displacement x.
Incorrect
According Hooke’s law, the restoring force developed in the spring is
The negative sign in the above expression implies that the spring force is always opposite to that of displacement x and k is the force constant. Therefore applied force is F_{a} = +kx. The positive sign implies that the applied force is in the direction of displacement x.

Question 37 of 75
37. Question
Which of this value is dependent on the spring force?
Correct
The spring force is an example of variable force as it depends on the displacement x. Let the spring be stretched to a small distance dx. The work done by the applied force on the spring to stretch it by a displacement x is stored as elastic potential energy.
Incorrect
The spring force is an example of variable force as it depends on the displacement x. Let the spring be stretched to a small distance dx. The work done by the applied force on the spring to stretch it by a displacement x is stored as elastic potential energy.

Question 38 of 75
38. Question
Choose the correct statements.
 i) The applied force and the displacement in the spring action are opposite to each other.
 ii) The initial position of the spring is taken as the equilibrium position or mean position.
Correct
The applied force F_{a} and the displacement dr (i.e., here dx ) are in the same direction. As, the initial position is taken as the equilibrium position or mean position, x=0 is the lower limit of integration.
Incorrect
The applied force F_{a} and the displacement dr (i.e., here dx ) are in the same direction. As, the initial position is taken as the equilibrium position or mean position, x=0 is the lower limit of integration.

Question 39 of 75
39. Question
To which of these values the potential energy of the spring does not depend?
Correct
The potential energy stored in the spring does not depend on the mass that is attached to the spring.
Incorrect
The potential energy stored in the spring does not depend on the mass that is attached to the spring.

Question 40 of 75
40. Question
Which of the value can be calculated by the Forcedisplacement graph?
Correct
Forcedisplacement graph for a spring: Since the restoring spring force and displacement are linearly related as F = – k x, and are opposite in direction, the graph between F and x is a straight line with dwelling only in the second and fourth quadrant. The elastic potential energy can be easily calculated by drawing a F – x graph. The shaded area (triangle) is the work done by the spring force.
Incorrect
Forcedisplacement graph for a spring: Since the restoring spring force and displacement are linearly related as F = – k x, and are opposite in direction, the graph between F and x is a straight line with dwelling only in the second and fourth quadrant. The elastic potential energy can be easily calculated by drawing a F – x graph. The shaded area (triangle) is the work done by the spring force.

Question 41 of 75
41. Question
What is the value of the energy of the spring in a frictionless environment?
Correct
In a frictionless environment, the energy gets transferred from kinetic to potential and potential to kinetic repeatedly such that the total energy of the system remains constant. At the mean position, ∆KE = ∆U
Incorrect
In a frictionless environment, the energy gets transferred from kinetic to potential and potential to kinetic repeatedly such that the total energy of the system remains constant. At the mean position, ∆KE = ∆U

Question 42 of 75
42. Question
Which of the value is dependent on the work done for a conservative force?
Correct
Conservative force: A force is said to be a conservative force if the work done by or against the force in moving the body depends only on the initial and final positions of the body and not on the nature of the path followed between the initial and final positions.
Incorrect
Conservative force: A force is said to be a conservative force if the work done by or against the force in moving the body depends only on the initial and final positions of the body and not on the nature of the path followed between the initial and final positions.

Question 43 of 75
43. Question
What is the value of the conservative force?
Correct
Whatever may be the path, the work done against the gravitational force is the same as long as the initial and final positions are the same. This is the reason why gravitational force is a conservative force. Conservative force is equal to the negative gradient of the potential energy.
Incorrect
Whatever may be the path, the work done against the gravitational force is the same as long as the initial and final positions are the same. This is the reason why gravitational force is a conservative force. Conservative force is equal to the negative gradient of the potential energy.

Question 44 of 75
44. Question
Which of the following is not a frictional force?
Correct
Examples for conservative forces are elastic spring force, electrostatic force, magnetic force, gravitational force, etc.
Incorrect
Examples for conservative forces are elastic spring force, electrostatic force, magnetic force, gravitational force, etc.

Question 45 of 75
45. Question
A Conservative force is,
 i) Work done is independent of the path.
 ii) Work done in a round trip is not zero.
 iii) Completely recoverable work done.
 iv) Total energy is dissipated as heat.
Correct
Incorrect

Question 46 of 75
46. Question
Which of the following is not true regarding the Nonconservative forces?
Correct
Incorrect

Question 47 of 75
47. Question
To which of this value the work done is dependent for a nonconservative force?
Correct
Nonconservative force: A force is said to be nonconservative if the work done by or against the force in moving a body depends upon the path between the initial and final positions. This means that the value of work done is different in different paths.
Incorrect
Nonconservative force: A force is said to be nonconservative if the work done by or against the force in moving a body depends upon the path between the initial and final positions. This means that the value of work done is different in different paths.

Question 48 of 75
48. Question
Which of the forces are classified as nonconservative forces?
Correct
Frictional forces are nonconservative forces as the work done against friction depends on the length of the path moved by the body. The force due to air resistance, viscous force are also nonconservative forces as the work done by or against these forces depends upon the velocity of motion.
Incorrect
Frictional forces are nonconservative forces as the work done against friction depends on the length of the path moved by the body. The force due to air resistance, viscous force are also nonconservative forces as the work done by or against these forces depends upon the velocity of motion.

Question 49 of 75
49. Question
Which of the energy is at highest point of an object thrown upwards?
Correct
Explanation
When an object is thrown upwards its kinetic energy goes on decreasing and consequently its potential energy keeps increasing (neglecting air resistance). When it reaches the highest point its energy is completely potential.
Incorrect
Explanation
When an object is thrown upwards its kinetic energy goes on decreasing and consequently its potential energy keeps increasing (neglecting air resistance). When it reaches the highest point its energy is completely potential.

Question 50 of 75
50. Question
What is the intermediate point value of an object falling from a height?
Correct
When the object falls back from a height its kinetic energy increases whereas its potential energy decreases. When it touches the ground its energy is completely kinetic. At the intermediate points the energy is both kinetic and potential.
Incorrect
When the object falls back from a height its kinetic energy increases whereas its potential energy decreases. When it touches the ground its energy is completely kinetic. At the intermediate points the energy is both kinetic and potential.

Question 51 of 75
51. Question
Choose the Incorrect statements.
 i) When an object reaches the ground from a height kinetic energy is stored as work done.
 ii) The energy transformation takes place at every point of travel from a height to ground.
 iii) By the law of conservation of energy the total mechanical energy remains constant.
Correct
When the body reaches the ground the kinetic energy is completely dissipated into some other form of energy like sound, heat, light and deformation of the body etc. In this example the energy transformation takes place at every point. The sum of kinetic energy and potential energy i.e., the total mechanical energy always remains constant, implying that the total energy is conserved. This is stated as the law of conservation of energy.
Incorrect
When the body reaches the ground the kinetic energy is completely dissipated into some other form of energy like sound, heat, light and deformation of the body etc. In this example the energy transformation takes place at every point. The sum of kinetic energy and potential energy i.e., the total mechanical energy always remains constant, implying that the total energy is conserved. This is stated as the law of conservation of energy.

Question 52 of 75
52. Question
What is the value of the total energy of an isolated system by the law of conservation?
Correct
The law of conservation of energy states that energy can neither be created nor destroyed. It may be transformed from one form to another but the total energy of an isolated system remains constant.
Incorrect
The law of conservation of energy states that energy can neither be created nor destroyed. It may be transformed from one form to another but the total energy of an isolated system remains constant.

Question 53 of 75
53. Question
Which of the following is not related to power?
Correct
Power is a measure of how fast or slow a work is done. Power is defined as the rate of work done or energy delivered. Power P = work done / time taken = W/ t
Incorrect
Power is a measure of how fast or slow a work is done. Power is defined as the rate of work done or energy delivered. Power P = work done / time taken = W/ t

Question 54 of 75
54. Question
The average power is the ratio between total work done to the total _______.
Correct
Average power: The average power (P_{av}) is defined as the ratio of the total work done to the total time taken. P_{av }= total work done / total time taken
Incorrect
Average power: The average power (P_{av}) is defined as the ratio of the total work done to the total time taken. P_{av }= total work done / total time taken

Question 55 of 75
55. Question
What is the value of the instantaneous power?
Correct
Instantaneous power: The instantaneous power (P _{inst}) is defined as the power delivered at an instant (as time interval approaches zero), P _{inst} = dW/dt
Incorrect
Instantaneous power: The instantaneous power (P _{inst}) is defined as the power delivered at an instant (as time interval approaches zero), P _{inst} = dW/dt

Question 56 of 75
56. Question
Choose the correct statements.
 i) Power is a vector quantity.
 ii) The dimension of power is ML^{2}T^{3}
 iii) The SI unit of power is watt (W).
Correct
Power is a scalar quantity. Its dimension is [ML^{2}T^{3}]. The SI unit of power is watt (W), named after the inventor of the steam engine James Watt. One watt is defined as the power when one joule of work is done in one second, (1 W = 1 J s–1).
Incorrect
Power is a scalar quantity. Its dimension is [ML^{2}T^{3}]. The SI unit of power is watt (W), named after the inventor of the steam engine James Watt. One watt is defined as the power when one joule of work is done in one second, (1 W = 1 J s–1).

Question 57 of 75
57. Question
Which of this value is not a higher unit of energy?
Correct
The higher units are kilowatt (kW), megawatt (MW), and Gigawatt (GW).
1kW = 1000 W = 10^{3}watt
1MW = 10^{6} watt
1GW = 10^{9} watt
Incorrect
The higher units are kilowatt (kW), megawatt (MW), and Gigawatt (GW).
1kW = 1000 W = 10^{3}watt
1MW = 10^{6} watt
1GW = 10^{9} watt

Question 58 of 75
58. Question
How many watts power is equal to one horse power?
Correct
For motors engines and some automobiles an old unit of power still commercially in use which is called as the horsepower (hp). We have a conversion for horsepower (hp) into watt (W) which is, 1 hp = 746 W
Incorrect
For motors engines and some automobiles an old unit of power still commercially in use which is called as the horsepower (hp). We have a conversion for horsepower (hp) into watt (W) which is, 1 hp = 746 W

Question 59 of 75
59. Question
In which of this unit the electrical energy is measured?
Correct
Measuring the electrical energy in a small unit watt second (W s) leads to handling large numerical values. Hence, electrical energy is measured in the unit called kilowatt hour (kWh).1 electrical unit = 1 kWh = 1 × (103 W) × (3600 s). 1 electrical unit = 3600×103 W s. 1 electrical unit = 3.6×106 J. 1 kWh = 3.6×106 J
Incorrect
Measuring the electrical energy in a small unit watt second (W s) leads to handling large numerical values. Hence, electrical energy is measured in the unit called kilowatt hour (kWh).1 electrical unit = 1 kWh = 1 × (103 W) × (3600 s). 1 electrical unit = 3600×103 W s. 1 electrical unit = 3.6×106 J. 1 kWh = 3.6×106 J

Question 60 of 75
60. Question
Calculate the energy consumed in electrical units when a 50 W fan is used for 5 hours daily for one month (30 days).
Correct
Electrical energy = power × time of usage = P × t = 50 x 240 watt hour = 12000 W h= 12kWh
1 electrical unit = 1kWh
Electrical energy unit =12
Incorrect
Electrical energy = power × time of usage = P × t = 50 x 240 watt hour = 12000 W h= 12kWh
1 electrical unit = 1kWh
Electrical energy unit =12

Question 61 of 75
61. Question
Match
 LED i) 1000hours
 Incandescent lamps ii) 6000 hours
 CFL iii) 50000 hours
Correct
Incandescent lamps glow for 1000 hours. CFL lamps glow for 6000 hours. But LED lamps glow for 50000 hrs (almost 25 years at 5.5 hour per day).
Incorrect
Incandescent lamps glow for 1000 hours. CFL lamps glow for 6000 hours. But LED lamps glow for 50000 hrs (almost 25 years at 5.5 hour per day).

Question 62 of 75
62. Question
Choose the correct statements.
 i) A Collision can happen only between two bodies with physical contacts.
 ii) Carom boards, Billiards and Marbles are example for collision
Correct
Collision is a common phenomenon that happens around us every now and then. For example, carom, billiards, marbles, etc. Collisions can happen between two bodies with or without physical contacts.
Incorrect
Collision is a common phenomenon that happens around us every now and then. For example, carom, billiards, marbles, etc. Collisions can happen between two bodies with or without physical contacts.

Question 63 of 75
63. Question
Which of this factor is changed during a collision time?
Correct
Linear momentum is conserved in all collision processes. When two bodies collide, the mutual impulsive forces acting between them during the collision time (Δt) produces a change in their respective momenta. That is, the first body exerts a forceF_{21 }on the second body. From Newton’s third law, the second body exerts a forceF_{12 }on the first body. This causes a change in momentum Δp_{1} and Δp_{2} of the first body and second body respectively.
Incorrect
Linear momentum is conserved in all collision processes. When two bodies collide, the mutual impulsive forces acting between them during the collision time (Δt) produces a change in their respective momenta. That is, the first body exerts a forceF_{21 }on the second body. From Newton’s third law, the second body exerts a forceF_{12 }on the first body. This causes a change in momentum Δp_{1} and Δp_{2} of the first body and second body respectively.

Question 64 of 75
64. Question
Which of the following is used to find the total momentum in collision?
Correct
The momentum is a vector quantity. Hence, vector addition has to be followed to find the total momentum of the individual bodies in collision.
Incorrect
The momentum is a vector quantity. Hence, vector addition has to be followed to find the total momentum of the individual bodies in collision.

Question 65 of 75
65. Question
Choose the correct statements.
 i) The Total linear momentum, total energy and the total kinetic energy are always conserved in a collision process.
 ii) The impact of collision and deformation due to collisions produce heat, sound, light energy.
 iii) The whole kinetic energy is transformed to other forms of energy after a collision.
Correct
In any collision process, the total linear momentum and total energy are always conserved whereas the total kinetic energy need not be conserved always. Some part of the initial kinetic energy is transformed to other forms of energy. This is because the impact of collisions and deformation occurring due to collisions may in general produce heat, sound, light etc.
Incorrect
In any collision process, the total linear momentum and total energy are always conserved whereas the total kinetic energy need not be conserved always. Some part of the initial kinetic energy is transformed to other forms of energy. This is because the impact of collisions and deformation occurring due to collisions may in general produce heat, sound, light etc.

Question 66 of 75
66. Question
How many types of collision are classified?
Correct
By taking these effects into account, we classify the types of collisions as follows: Elastic collision, Inelastic collision.
Incorrect
By taking these effects into account, we classify the types of collisions as follows: Elastic collision, Inelastic collision.

Question 67 of 75
67. Question
What is the condition required for an elastic collision?
Correct
Elastic collision: In a collision, the total initial kinetic energy of the bodies (before collision) is equal to the total final kinetic energy of the bodies (after collision) then, it is called as elastic collision. i.e., Total kinetic energy before collision = Total kinetic energy after collision
Incorrect
Elastic collision: In a collision, the total initial kinetic energy of the bodies (before collision) is equal to the total final kinetic energy of the bodies (after collision) then, it is called as elastic collision. i.e., Total kinetic energy before collision = Total kinetic energy after collision

Question 68 of 75
68. Question
Choose the incorrect statements.
 i) In an inelastic collision the total kinetic energy of the bodies is not equal to the total kinetic energy of the bodies.
 ii) Both the total energy and the kinetic energy and the losses are conserved in a inelastic collision.
Correct
Inelastic collision: In a collision, the total initial kinetic energy of the bodies (before collision) is not equal to the total final kinetic energy of the bodies (after collision) then, it is called as inelastic collision. Total kinetic energy before collision ≠ Total kinetic energy after collision. Even though kinetic energy is not conserved but the total energy is conserved. This is because the total energy contains the kinetic energy term and also a term ΔQ, which includes all the losses that take place during collision.
Incorrect
Inelastic collision: In a collision, the total initial kinetic energy of the bodies (before collision) is not equal to the total final kinetic energy of the bodies (after collision) then, it is called as inelastic collision. Total kinetic energy before collision ≠ Total kinetic energy after collision. Even though kinetic energy is not conserved but the total energy is conserved. This is because the total energy contains the kinetic energy term and also a term ΔQ, which includes all the losses that take place during collision.

Question 69 of 75
69. Question
Which of the following is known as complete or perfect inelastic collision?
Correct
The loss in kinetic energy during collision is transformed to another form of energy like sound, thermal, etc. Further, if the two colliding bodies stick together after collision such collisions are known as completely inelastic collision or perfectly inelastic collision. Such a collision is found very often. For example when a clay putty is thrown on a moving vehicle, the clay putty (or Bubblegum) sticks to the moving vehicle and they move together with the same velocity
Incorrect
The loss in kinetic energy during collision is transformed to another form of energy like sound, thermal, etc. Further, if the two colliding bodies stick together after collision such collisions are known as completely inelastic collision or perfectly inelastic collision. Such a collision is found very often. For example when a clay putty is thrown on a moving vehicle, the clay putty (or Bubblegum) sticks to the moving vehicle and they move together with the same velocity

Question 70 of 75
70. Question
Which of the following is not true regarding the Elastic collision?
Correct
Incorrect

Question 71 of 75
71. Question
Choose the correct statements regarding the Inelastic collision.
 i) Nonconservative forces are involved.
 ii) Mechanical energy is not dissipated.
 iii) Total kinetic energy is conserved.
Correct
Incorrect

Question 72 of 75
72. Question
What is the dimension of the coefficient of restitution?
Correct
Total kinetic energy before collision: The amount of kinetic energy after the collision of two bodies, in general can be measured through a dimensionless number called the coefficient of restitution (COR)
Incorrect
Total kinetic energy before collision: The amount of kinetic energy after the collision of two bodies, in general can be measured through a dimensionless number called the coefficient of restitution (COR)

Question 73 of 75
73. Question
Which of this relative factor is accounted for calculating the Coefficient of restitution?
Correct
Coefficient of restitution (COR) is defined as the ratio of velocity of separation (relative velocity) after collision to the velocity of approach (relative velocity) before collision.
Incorrect
Coefficient of restitution (COR) is defined as the ratio of velocity of separation (relative velocity) after collision to the velocity of approach (relative velocity) before collision.

Question 74 of 75
74. Question
Choose the correct statements.
 i) In ideal condition the value of restitution coefficient is equal to zero.
 ii) In any real collision both the potential and kinetic energy have some losses.
 iii) If the velocity separation is zero after a collision then the value of coefficient of restitution is also zero.
Correct
In any real collision problems, there will be some losses in kinetic energy due to collision, which means e is not always equal to unity. If the ball is perfectly plastic, it will never bounce back and therefore their separation of velocity is zero after the collision. Hence, the value of coefficient of restitution, e = 0.
Incorrect
In any real collision problems, there will be some losses in kinetic energy due to collision, which means e is not always equal to unity. If the ball is perfectly plastic, it will never bounce back and therefore their separation of velocity is zero after the collision. Hence, the value of coefficient of restitution, e = 0.

Question 75 of 75
75. Question
What is the range of the restitution coefficient value of a material?
Correct
In general, the coefficient of restitution for a material lies between 0 < e <1.
Incorrect
In general, the coefficient of restitution for a material lies between 0 < e <1.
Leaderboard: Work, Energy and Power 11th Science Lesson
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