## Physics - Force and Pressure, Friction and Universe (Revision Sheet)

1. What is the necessity of pressurized cabins and airplanes?

2. You are provided with two surfaces, one smooth and one rough or uneven. Try to stick a rubber sucker on both the surfaces. Will you succeed in doing so? Give reasons for your answer.

3. Can a scuba diver dive into the ocean wearing ordinary clothes? Why or why not?

4. Why do some people experience nasal bleeding at high altitudes?

5. Explain Why, it is easier to drag a mat on floor when nobody is sitting on it but much more difficult to drag the same mat when a person is sitting on it.

6. Name the type of force in the following cases.

(a) Force exerted between heavenly bodies.
(b) Force to pull a heavy object.
(c) Force that slows down moving objects.
(d) Force due to charged particles.

7. What will happen to a moving body if there is no friction acting on it?

8. Give reasons.

(a) Sportsman use shoes with spikes.
(b) It is difficult to walk on loose sand.
(c) Ball bearings are used in machinery.

9. Tyres of a truck have grooves whereas tyres of formula racing cars are smooth. What could be the reason behind this?

10. Objects moving in fluids have a special shape. What shape it is? Why is it used?

11. Friction is a necessary evil. Comment on it.

12. What causes friction between two surfaces?

13. Explain why:

(a) a pencil will write on paper but not on glass.
(b) The handles of motor cycle are covered with a rubber sheet with spikes.
(c) The soles of our shoes wear out gradually.
(d) Tyres of car wear out gradually.

14. What kind of friction comes into play:

(a) When a block of wood kept on table moves slowly?
(b) When a block of wood kept on table just tends to move (or slip)
(c) When a block of wood kept on cylindrical iron rods moves?

15. Out of sliding friction, static friction & rolling friction:

(a) Which one is the smallest?
(b) Which one is the largest?

16. The earth revolves around the sun. Can we call earth a satellite of the Sun?

17. Why can’t we see stars during the day?

18. Mercury is closest to the Sun but Venus is the hottest planet. Why?

19. What are asteroids? Where are they found?

20. What are comets? How would you identify a comet? Name any one comet with its orbital period.

21. If there would have been life on Venus and you were staying on it in which direction would the Sun rise and set? Will it be same as on Earth? Give reason for your answer.

22. If Moon had an atmosphere how different would it be from the present one?

23. How long would it take for us to see the other side of the satellite Moon?