NCERT Solutions: Motion & Measurement of Distances

# NCERT Solutions for Class 8 Science Chapter 7 - Motion and Measurement of Distances

Q1. Give two examples each, of modes of transport used on land, water and air.
Ans:
Land transport: Bus, train, motorbike.
Water transport: Boat, Ship, steamer.
Air Transport: Aeroplane, Helicopter.

Q2. Fill in the blanks:
(i) One metre is ______________ cm.
(ii) Five kilometres is ______________ m.
(iii) Motion of a child on a swing is ______________.
(iv) Motion of the needle of a sewing machine is ______________.
(v) Motion of wheel of a bicycle is______________.
Ans:
(i) One metre is 100 cm.
(ii) Five kilometres is 5000 m.
(iii) The motion of a child on a swing is periodic motion.
(iv) The motion of the needle of a sewing machine is periodic motion.
(v) The motion of the wheel of a bicycle is circular motion.

Q3. Why can a pace or a footstep not be used as a standard unit of length?
Ans: A pace or a footstep not be used as a standard unit of length because the size of a pace and footstep vary from person to person. This will lead to confusion while measuring the lengths by different persons. We should use standard units like the International System of Units (SI Units).

Q4. Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
Ans: 1 millimetre, 1 centimetre, 1 metre, 1 kilometre

Q5. The height of a person is 1.65 m. Express it into cm and mm.
Ans:  We know that,
1 metre = 100 cm
1 metre = 1000 mm
So, 1.65 m = 1.65 × 100
= 165 cm
1.65 m = 1.65 × 1000
= 1650 mm

Q6. The distance between Radha's home and her school is 3250 m. Express this distance into km.
Ans: We know that 1 m = 1/1000 km
So, 3250 m = 3250/1000 km
= 3.25 km

Q7. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?
Ans: The length of the needle = 33.1 cm – 3.0 cm = 30.1 cm

Q8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Ans:
Similarity: The blades of a fan and the wheels of a bicycle show circular motion.
Difference: Bicycles move in rectilinear motion, but the fan does not move in rectilinear motion.

Q9. Why would you not like to use a measuring tape made of an elastic material like rubber to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with such a tape?
Ans: An elastic measuring tape will not give accurate measurements as it stretches in length and reduces in size when stretched. When we express measurements taken with elastic tape, we have to tell whether the tape was stretched. If yes, how much? Hence, it is very difficult to tell the measurement taken from an elastic tape.

Q10. Give two examples of periodic motion.
Ans:

• Rotation of Earth
• Motion of Pendulum
• Vibrating wire of the guitar, etc.

Any two examples can be used.

The document NCERT Solutions for Class 8 Science Chapter 7 - Motion and Measurement of Distances is a part of the Class 6 Course Science Class 6.
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## FAQs on NCERT Solutions for Class 8 Science Chapter 7 - Motion and Measurement of Distances

 1. What is motion and how is it related to the measurement of distances?
Ans. Motion refers to the change in position of an object with respect to time. The measurement of distances is closely related to motion as it helps in quantifying the extent of motion. By measuring the distance traveled by an object, we can determine the magnitude of its motion.
 2. How do we measure distance?
Ans. Distance can be measured using various methods such as using a ruler or a measuring tape for shorter distances, or using odometers, GPS devices, or even satellite-based technologies for longer distances. The choice of measurement method depends on the accuracy and precision required for the specific situation.
 3. What are the different units used to measure distance?
Ans. Distance can be measured using various units such as meters (m), kilometers (km), centimeters (cm), millimeters (mm), etc. The choice of unit depends on the magnitude of the distance being measured. For example, we use kilometers for longer distances and centimeters or millimeters for shorter distances.
 4. What is the difference between distance and displacement?
Ans. Distance refers to the total path traveled by an object, regardless of its direction. On the other hand, displacement refers to the shortest distance between the initial and final positions of an object, considering both magnitude and direction. Displacement takes into account the change in position, while distance does not consider direction.
 5. How does the measurement of distances help in various fields and everyday life?
Ans. The measurement of distances plays a crucial role in various fields and everyday life. It helps in navigation, transportation, construction, sports, scientific research, and many other aspects of our lives. Accurate measurement of distances is essential for planning, designing, and executing various activities, ensuring efficiency and precision in our actions.

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