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

Answer:

- On land transport: Car and Bus
- Water Transport: Ship and Boat
- Air transport: Aeroplane and Helicopter

2. Fill in the blanks:

(i) One metre is ___100___________ cm.

(ii) Five kilometre is ______5000________ m.

(iii)Motion of a child on a swing is _______periodic motion_______.

(iv) Motion of the needle of a sewing machine is ________periodic motion( up and down)______.

(v) Motion of wheel of a bicycle is__circular_______.

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

Answer:

- Because footstep varies from human to human; It is not standard. The standard unit of length does not change from person to person.

4. Arrange the following lengths in their increasing magnitude:

1 meter, 1 centimeter, 1 kilometer,1 millimeter.

Answer:

The following are arranged in increasing magnitude:

- 1 millimeter
- 1 centimeter
- 1 meter
- 1 kilometer

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

Answer:

As we know that :

- 1 meter=100 centimeter;
- 1 meter=1000 millimeter

Hence :

1.65 m=1.65*100cm=165 cm.

1.65m=1.65*1000 mm=1650 mm.

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

Answer:

As we know that:

1 km=1000m, so

1 m=1/1000 km.

Distance between Radha's home and her school is 3250 m.

3250 m=3250/1000 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:

The length of the needle would be=33.1-3.0=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:
- Wheel of bicycle and ceiling fan move in circulation motion.
- Difference:
- A fan-only move in circulation motion but does not perform rectilinear motion while bicycle motion is rectilinear along with the circular motion of its wheels.

9. 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?

Answer:

- It would not give accurate measures as the length of elastic material get changes while stretching.

10. Give two examples of periodic motion.

Answer:

The following are two examples:

- Pendulum
- String of Guitar
- the membrane of tabla( drums)

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