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Measurement Book Back Questions 7th Science Lesson 1

7th Science Lesson 1

1] Measurement

Book Back Questions with Answer and Do You Know Box Content

Do You Know?

One square metre is the area enclosed inside a square of side 1 metre.

Problem 1.1: What is the area of a 10 square each of side of 1 m.

Solution: Area of a square = side x side

= 1 m x 1 m = 1m2 or 1 square metre

Area of 10 squares = 1 square metre x 10 = 10 square metre

(Even though the area is given in square metre, the surfaces need not to be square in shape)

Problem 1.2: Find the area of the following regular shaped figures: (Take π = 22/7). (a) A rectangle whose length is 12 m and breadth is 4 m. (b) A circle whose radius is 7 m. (c) A triangle whose base is 6 m and height is 8 m.

Solution: (a) Area of rectangle = length x breadth = 12 x 4 = 48 m2

(b) Area of circle = π x r2 = (22/7) x 7 x 7 = 154 m2

(c) Area of triangle = (1/2) x base x height = (1/2) x 6 x 8 = 24 m2

Problem 1.3: Find the volume of (Take π = 22/7). (i) a cube whose side is 3 cm. (ii) a cylinder whose radius is 3 m and height is 7 m.

Solution: (a) Volume of a cube = side x side x side = 3 cm x 3 cm x 3 cm = 27 cubic cm or cm3.

(b) Volume of a cylinder = π x r2 x height = (22/7) x 3 x 3 x 7 = 198 m3.

To measure the volume of liquids, some other units are also used, some of them are gallon ounce and quart.

1 gallon = 3785 ml

1 ounce = 30 ml

1 quart = 1 litre

Problem 1.4: A solid cylinder of mass 280 kg has a volume of 4 cm3. Find the density of cylinder.

Solution: Density of cylinder = mass of cylinder/volume of cylinder = 280/4 = 70 kg/m3

Problem 1.5: A box is made up of iron and it has a volume of 125 cm3. Find its mass. (Density of iron is 7.8 g/cm3).

Solution: Density = Mass/Volume

Hence, Mass = Volume x Density = 125 x 7.8 = 975 g.

Problem 1.6: A sphere is made from copper whose mass is 3000 kg. If the density of copper is 8900 kg/m3, find the volume of the sphere.

Solution: Density = Mass/Volume

Hence, Volume = Mass/Density = 3000/8900 = 30/89 = 0.34 m3.

Water has more density than oils like cooking oil and castor oil, although this oil appears to be denser than water. Density of castor oil is 961 kg/m3. If we put one drop of water in oil, water drop sinks. But, if we put one drop of oil in water, oil floats and forms a layer on water surface. However, some oils are denser than water.

Choose the best answers:

1. Which of the following is a derived unit?

(a) Mass

(b) Time

(c) Area

(d) Length

2. Which of the following is correct?

(a) 1L = 1 cc

(b) 1L = 10 cc

(c) 1L = 100 cc

(d) 1L = 1000 cc

3. SI unit of density is

(a) kg/m2

(b) kg/m3

(c) kg/m

(d) g/m3

4. Two spheres have equal mass and volume in the ratio 2:1. The ratio of their density is

(a) 1:2

(b) 2:1

(c) 4:1

(d) 1:4

5. Light year is the unit of

(a) Distance

(b) Time

(c) Density

(d) Both length and time

Fill in the blanks:

1. Volume of irregularly shaped objects is measured using the law of ______________

2. One cubic metre is equal to ______________ cubic centimetre.

3. Density of mercury is ______________

4. One astronomical unit is equal to _______________

5. The area of a leaf can be measured using a _____________

State true or false. If false, correct the statement:

1. The region covered by the boundary of the plane figure is called its volume.

2. Volume of liquids can be found using measuring containers.

3. Water is denser than kerosene.

4. A ball of iron floats in mercury.

5. A substance which contains less number of molecules per unit volume is said to be denser.

Match the items in column – I to the items in column II:

(1)

Column I – Column II

i. Area – (a) light year

ii. Distance – (b) m3

iii. Density – (c) m2

iv. Volume – (d) kg

v. Mass – (e) kg/m3

(2)

Column I – Column II

i. Area – (a) g/cm3

ii. Length – (b) measuring jar

iii. Density – (c) amount of a substance

iv. Volume – (d) rope

v. Mass – (e) plane figures

Arrange the following in correct sequence:

1. 1L, 100 cc, 10 L, 10 cc

2. Copper, Aluminium, Gold, Iron

Complete the analogy:

1. Area: m2 :: Volume: ________________

2. Liquid: Litre :: Solid: ______________

3. Water: Kerosene :: ______________: Aluminium

Consider the statements given below and choose the correct option:

Mark the correct choice as

(a) If both assertion and reason are true and reason is the correct explanation of assertion

(b) If both assertion and reason are true but reason is not the correct explanation of assertion

(c) If assertion is true but reason is false

(d) If assertion is false but reason is true

1. Assertion: Volume of a stone is found using a measuring cylinder.

Reason: Stone is an irregularly shaped object.

2. Assertion: Wood floats in water.

Reason: Water is a transparent liquid.

3. Assertion: Iron ball sinks in water.

Reason: Water is denser than iron.

Answers:

Choose the correct answers:

1. Area 2.1L=1000 cc 3. Kg/m3 4. 2:1 5. Distance

Fill in the blanks:

1. Archimedes 2.100 3.13600kg/m3 4.1.496 x 1011m 5. Graphical method

State True or False:

1. False

Correct Statement: The region covered by the boundary of the plane figure is called its area.

2. True

3. True

4. True

5. False

Correct Statement: A substance which contains more number of molecules per unit volume is said to be denser.

Match the following:

1.i. m2 ii. Light year iii. Kg/m3 iv. m3 v.kg

2.i. Plane figures ii. Rope iii. g/cm3 iv. Measuring jar v. Amount of a substance

Arrange the following in correct sequence:

1. 10 cc, 100cc, 1L, 10L

2. Aluminium, Iron, Copper, Gold

Complete the analogy:

1. m3 2. Cubic metre 3. Iron

Consider the statements given below and choose the correct option:

1.Assertion is false but reason is true.

2.Both assertion and reason are true and reason is the correct explanation of assertion.

3.Assertion is true but reason is false.

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