Force And Motion Book Back Questions 7th Science Lesson 2
7th Science Lesson 2
2] Force And Motion
Book Back Questions with Answer and Do You Know Box Content
Do You Know?
Nautical mile: Nautical mile is the unit for measuring the distance in the field of aviation and sea transportation. One nautical mile is 1.852 km. The unit for measuring the speed of aeroplane and ships is knot. One knot is the speed taken to travel one nautical mile in hour.
1 km/h = 5/18 m/s. How we got this?
1 km = 1000 m
1 h = 3600 s
1 km/h = 1000 m/3600 s = 5/18 m/s
Cheetah: My name is cheetah. I can run at a great speed. Do you know what my speed is? 25 m/s to 30 m/s. My speed changes from 0 to 20 m/s in 2 seconds. See how good my acceleration is!
Choose the best answers:
1. A particle is moving in a circular path of radius r. The displacement after half a circle would be
(a) Zero
(b) R
(c) 2 r
(d) r/2
2. From the given v-t graph it can be inferred that the object is
(a) In uniform motion
(b) At rest
(c) In non uniform motion
(d) Moving with uniform acceleration
3. Which of the following figures represent uniform motion of a moving object correctly?
4. Suppose a boy is enjoying a ride on a merry go round which is moving with a constant speed of 10 m/s. It implies that the boy is
(a) At rest
(b) Moving with no acceleration
(c) In accelerated motion
(d) Moving with uniform velocity
5. What is one way you might increase the stability of an object?
(a) Lower the centre of gravity
(b) Raise the centre of gravity
(c) Increase the height of the object
(d) Shorten the base of the object
Fill in the blanks:
1. The shortest distance between the two places is _____________
2. The rate of change of velocity is ____________
3. If the velocity of an object increases with respect to time, then the object is said to be in ___________ acceleration.
4. The slope of the speed-time graph gives ________________
5. In ___________________ equilibrium its centre of gravity remains at the same height when it is displaced.
Match the following:
1. Displacement – Knot
2. Light travels through vacuum – Geometric centre
3. Speed of ship – Metre
4. Centre of gravity of the geometric shaped object – Larger base area
5. Stability – Uniform velocity
Complete the analogy:
1. Velocity: metre/second :: acceleration: ________________
2. Length of scale: metre :: speed of aeroplane: _______________
3. Displacement/time: velocity :: speed/time: ________________
Answers:
Choose the correct answers:
1. 2R 2. In uniform motion 3. 
4. Moving with no acceleration 5. Lowers the centre of gravity
Fill in the blanks:
1. Straight path 2. Acceleration 3. Positive 4. Acceleration 5. Neutral
Match the following:
1. Metre 2. Uniform velocity 3. Knot 4. Geometric centre 5. Larger base area
Complete the analogy:
1. metre/ s2 2. Knot 3. Distance