Living Science Physics Class 7 ICSE Solutions Chapter 1 Physical Quantities and Measurement

ICSE Living Science Physics for Class 7 Solutions Chapter 1 Physical Quantities and Measurement

Check Your Progress (Page 8)

A. Write true or false. Correct the false statements.
Question 1.
The total space occupied by an object is called its area.
Answer:
False.

Question 2.
The total space occupied by an object is called its volume. We can find the area of irregular figures using a graph paper.
Answer:
True.

Question 3.
The maximum volume of a liquid that a container can hold is known as its capacity.
Answer:
True.

Question 4.
Conical measuring cans with long handles are commonly used to measure milk.
Answer:
False. Cylindrical measuring cans with long handles are commonly used to measure milk.

Question 5.
Measuring cans used for commercial purposes have fixed capacities.
Answer:
True.

B. Solve the following numerical problems.

Question 1.
The length and breadth of a park is 60 m and 40 m respectively. Find its area.
Answer:
Area of the park = Length x Breadth = 60 m x 40 m = 2400 m²

Question 2.
Find the volume of an ice-cream brick of length 22 cm, breadth 10 cm and height 8 cm.
Answer:
Volume of the ice cream brick = Length x Breadth x Height = 22 cm x 10 cm x 8 cm = 1760 cm³

Question 3.
Find the volume of 20 ice cubes, each of side 5 cm.
Answer:
Volume of 1 ice cube = (side)³
= 5 cm x 5 cm x 5 cm = 125 cm³

Question 4.
How many litres of water will a cubical vessel hold if its side measures 50 cm?
Answer:
Volume of a cube = (side)³
= 50 x 50 x 50
= 125000 cm³
= 125000 mL
= 125 L

Think And Answer (Page 8)
How will you measure the volume of an irregular solid which floats on water (a piece of wood)?
Answer:
We can measure the volume of an irregular solid by using a measuring cylinder.

A. Tick the most appropriate answer.

Question 1.
The region enclosed within the boundaries of a closed figure is known as its
a. length.
b. area,
c. volume.
d. mass.
Answer:
b. area.

Question 2.
The total space occupied by an object is called its
a. mass.
b. volume.
c. density.
d. speed.
Answer:
b. volume.

Question 3.
Which of the following device is commonly used to measure the volume of liquids such as petrol or kerosene?
a. measuring cup
b. spring balance
c. conical cans
d. cylindrical cans
Answer:
c. conical cans

Question 4.
The density of a substance is the ratio of its mass to
a. weight.
b. volume.
c. area.
d. temperature.
Answer:
b. volume.

Question 5.
Which of the following physical quantity is used to describe the motion of a body?
a. area
b. volume
c. density
d. speed
Answer:
d. speed

Question 6.
Which of the following relation is correct?
a. speed = distance x time
b. distance = speed x time
c. time = distance x speed

Answer:
b. distance = speed x time

B. Fill in the blanks.

Question 1.
The SI unit of area is …………
Answer:
The SI unit of area is m² (square metre).

Question 2.
The area of a leaf can be found by using a ………..
Answer:
The area of a leaf can be found by using a graph paper.

Question 3.
Each unit of space in a solid figure is taken as a …………. cube.
Answer:
Each unit of space in a solid figure is taken as a unit cube.

Question 4.
Liquids do not have a …………. shape.
Answer:
Liquids do not have a fixed shape.

Question 5.
The ………….. of a substance is the ratio of its mass to volume.
Answer:
The density of a substance is the ratio of its mass to volume.

Question 6.
The distance travelled by a body in unit time is known as its ………….
Answer:
The distance travelled by a body in unit time is known as its speed.

Question 7.
The speed of fast-moving objects are expressed in ………..
Answer:
The speed of fast-moving objects are expressed in kilometre per hour (km/h).

C. Match the columns.

Answer:

D. Answer the following in short.

Question 1.
What do you understand by the term area?
Answer:
The amount of surface enclosed by a plane figure is called its area.

Question 2.
What do you understand by the term capacity?
Answer:
The maximum volume of a liquid that a container can hold is known as its capacity.

Question 3.
Define density of a substance. State the unit of density in the SI system.
Answer:
Density of a substance is defined as the volume of a body is the total three-dimensional space occupied by it. The SI unit of density is kg/m^-3 or km m^-3.

Question 4.
Why is iron heavier than wood for the same volume?
Answer:
Iron is heavier than wood for the same volume because the density of iron is greater than that of wood.

Question 5.
Define speed. Write its SI unit.
Answer:
The distance travelled by a body in unit time is known as its speed. The SI unit of speed is metre per second (m/s).

E. Answer the following in detail.

Question 1.
Explain how you would measure the area of an irregular shape using a graph paper.
Answer:
Irregular shapes do not have easily measurable dimensions. However, we can indirectly find the area of an irregular surface using a graph paper. Place a leaf on a graph paper and trace its outline with the help of a pencil. Remove the leaf. Now count the number of complete squares within the outline.

Also count the number of incomplete squares that are half or more than half within the outline. Ignore the number of squares that are less than half. The area of the leaf = (Number of complete squares) cm² + (Number of half or more-than-half squares) cm².

Question 2.
Write a short note on some devices that are used to measure the volume of liquids.
Answer:
The volume of a liquid is usually measured by measuring cans of different shapes and sizes. Measuring cans are available in capacities ranging from 50 mL to 5 L. Conical measuring cans are used to measure liquids such as kerosene and petrol. Cylindrical measuring cans with long handles are commonly used to measure milk and edible oil.

Question 3.
Describe a method by which you can measure the volume of an irregular solid.
Answer:
Aim : To measure the volume of an irregular shaped stone. Materials Required : Some water, a measuring cylinder, a string and a small stone.

Procedure : Pour some water in the measuring cylinder and read its level from the scale marked on the wall of the cylinder. Now tie the string around a stone and lower it into the cylinder without touching its walls until it is completely immersed in water. The level of water in the cylinder rises as the stone is immersed in it. Read the level of water again.

Observation and conclusion : Initial reading of the water level = 80 mL (say) Final reading of the water level = 130 mL.
Hence, the volume of the stone = 130 mL – 80 mL = 50 mL.

Question 4.
How can we compare the fastness or slowness of two moving objects?
Answer:
We can compare the fastness or slowness of two moving objects in terms of speed. For example, if we see a car running fast, we say that its speed is fast and if we see a bicycle moving slow, we say that its speed is slow.

Question 5.
How will you calculate the distance covered by a body if its speed and time taken are given?
Answer:
If an object travels for time t at speed v, it covers a distance given by s = v x t.

F. Solve the following numerical problems.

Question 1.
Calculate the density of a solid of mass 20 kg if it occupies a volume of 4 m³.
Answer:
Mass of solid = 20 kg
Volume = 4 m³
Density = \(\frac {M}{V}\) = \(\frac {20}{4}\)b = 5 kg/m³

Question 2.
The density of copper is 8.4 g cm3. What will be the volume of 200 gm of copper?
Answer:
Density of copper = 8.4 g cm³
Mass = 200 g
V = \(\frac {M}{D}\) = \(\frac {200}{8.4}\) = 23.8 cm³

Question 3.
Find the mass of 50 cm3 of silver if its density is 10.5 g cm^-3.
Answer:
Mass of silver = ?
Volume = 50 cm^-3
Density = 10.5 g cm^-3
M = D x V = 50 x 10.5 = 525 g

Question 4.
A rectangular piece of wood measures 4 cm by 6 cm by 8 cm and has a mass of 20 g. What is the density of the piece of wood ?
Answer:
Volume of the piece of wood = (4 x 6 x 8) cm³ = 192 cm³
Mass of the piece = 20 g

\(\frac{20 \mathrm{~g}}{192 \mathrm{~cm}^{3}}\) = 0,104 g cm^-3
Relative density of wood

= 0.104

Question 5.
Calculate the speed of an object if it covers 200 metres in 50 seconds.
Answer:

Speed = \(\frac {200}{50}\) = 4 m/s

Question 6.
An express train moves at a speed of 60 km h_1. How far will it travel in 3 h?
Answer:
Distance = Speed x Time
Distance = 60 x 3 = 180 km

Question 7.
How long will it take an object moving with a speed of 5 m/s to cover a distance of 20 m?
Answer:

Time = \(\frac {20}{5}\) = 4s

Question 8.
A train covers a distance of 820 km with a speed of 80 km/h. How long does it take to finish the journey?
Answer:
= \(\frac {820}{80}\) = 10.25 hours

G. Find the area of these leaves, if 1 square on the graph paper represents 1 cm².

1. The area of leaf 1
= (Number of complete squares) cm² + (Number of half or more than half squares) cm²
= 3 cm² + 5 cm²
= 3 cm² + 5 cm² = 8 cm²

2. The area of leaf 2
= (Number of complete squares) cm² + (Number of half or more than half squares) cm²
= 3 cm² + 6 cm²
= 3 cm² + 6 cm² = 9 cm²

3. The area of leaf 3
= (Number of complete squares) cm² + (Number of half or more than half squares) cm²
= 8 cm² + 8 cm²
= 8 cm² + 8 cm² = 16 cm²

4. The area of leaf 4
= (Number of complete squares) cm² + (Number of half or more than half squares) cm²
= 6 cm² + 8 cm²
= 6 cm² + 8 cm² = 14 cm²

5. The area of leaf 5
= (Number of complete squares) cm² + (Number of half or more than half squares) cm²
= 6 cm² + 9 cm²
= 6 cm² + 9 cm² = 15 cm²

H. Look at the following figure (next page) and answer the questions based on it.

Question 1.
Name the device used in the given figure.
Answer:
Measuring cylinder.

Question 2.
Find the volume of the stone.
Answer:
50 mL or 50 cm².

Question 3.
Find the density of the stone.
Answer:

\(\frac{250 \mathrm{~g}}{50 \mathrm{~cm}^{3}}\) = 5 g cm^-3

I. Answer the questions based on the following figures.

Question 2.
How much time will car 2 take to complete 600 m?
Answer:
Speed of car 2 = \(\frac {200}{5}\) m s^-2 = 40 m s^-1
Time taken by it to cover 600 m = \(\frac {600}{40}\)s = 15 s

Question 3.
How far would car 3 run in one minute?
Answer:
Speed of car 3 = \(\frac {600}{40}\) ms^-1 = 50 ms^-1
Distance covered by it in 1 minute = 50 x 60 m = 3000 m = 3 km

Think And Answer

Question 1.
Can we measure the volume of a regular solid using a measuring cylinder?
Answer:
Yes, we can also measure the volume of a regular solid using a measuring cylinder.

Question 2.
The density of a substance can tell about its purity. True or false? Explain.
Answer:
True. If we know the density of a pure substance, we can compare it with the density of the given substance.

Question 3.
The figure given below shows the distance travelled by 2 bodies in certain time. What will you conclude from this figure?

Answer:
From the given graph, we can see that Body 2 covers more distance than Body 1 in the same time interval. Hence, we can conclude that speed of Body 2 is more than that of Body 1.

Living Science Physics Class 7 ICSE Solutions