Chapter 10: Motions and Measurements of distances (Solutions)
Posted on : 26-02-2020 Posted by : Admin

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EXCERCISE

1. Give two examples of modes of transport used on land, water and air

Answer:

Land: Bike, Train

Water: Submarine, Ship

Air: Helicopter, Airplane

2. Fill in the blanks:

  1. One metre is 100cm.
  2. Five kilometers is 5000m.
  3. Motion of a child on a swing is circular motion.
  4. Motion of a needle of a sewing machine is periodic motion.
  5. Motion of a wheel of a bicycle is circular motion.

3. Why can a pace or a footstep not be used as a standard unit of length?

Answer: A pace or a footstep cannot be used as a standard unit of length as it is not same for every person. A standard unit must be same for everyone.

4. Arrange the following lengths in their increasing magnitude:

1 metre, 1 centimetre, 1 kilometre, 1 millimetre

Answer: 1 millimetre, 1 centimetre, 1 metre, 1 kilometre.

5. The height of a person is 1.65 m. Express it into cm and mm.

Answer: 1 meter = 100 cm and 1 meter = 1000 mm

Here, the height of a person is 1.65 m.

So,

the height of this person expressed in cm is 1.65 x 100 = 165 cm

the height of this person expressed in mm is 1.65 x 1000 = 1650 mm

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6. The distance between Radha's home and her school is 3250 m. Express this distance into km.

Answer: 1 meter = 0.001 km

Here,

the distance between Radha’s home and school is 3250 m.

So, 3250 m=3250 x 0.001 km

=3.25km

7. 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?

Answer: Difference between the readings at two ends of the measuring scale will give the exact length of the needle. The reading of the needle at one end is 3.0 cm while the reading at the other end is 33.1 cm.

So length of the needle is 33.1-3.0 cm=30.1 cm

8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

Answer: Similarities: Both the wheel of a bicycle and the blades of the ceiling fan undergo circular motion.

Differences: A cycle has translation motion but a ceiling fan does not have translation motion.

9. Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape?

Answer: We cannot use an elastic measuring tape to measure the distance. It would not give a perfect measurement as it stretches and contracts in size. When telling someone about a distance measured with an elastic tape we must specify how much the tape was stretched or contracted during the time of measurement. This would be a difficult job.

10. Give two examples of periodic motion.

Answer:

  1. Motion of a Pendulum
  2. Motion of the Earth round the Sun

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