FRICTION 8

 Practice Paper

Subject Physics(2019)

Class VIII                                  Ch- Friction                                              

1. Define friction.
2. What is force of friction?
3. What is the cause of friction?How can it be minimised?
4. Friction is required for walking. Explain.
5. What is rolling friction?
6. What is sliding friction?
7. What do you mean by the term drag?
8. What is the direction of frictional force?
9. Give one difference between frictional force and gravitational force.
10. Frictional force is used to stop a moving bicycle. How?
11. State the factors on which friction depends?
12. Why does a ball rolling along the ground stop after some time?
13. Why kabaddi players rub their hands with soil while playing?
14. Give reasons for the following: (a) Sparks are produced when a pair of scissors is sharpened against a grinding wheel. (b) A piece of chalk wears out as it is used on a black board.
15. Wet surfaces are more slippery. Give reason.
16. How is the force of friction on a body in a fluid minimised?
17. Explain, why a hovercraft travels much faster than a streamer pushing through water? 
18. State the factors on which drag depends.
19. Give reasons.(a) Powder is applied to a carom board.(b) A man walking on a street slips on a banana skin.(c) Oil is applied to the moving part of a machine.
20. Friction produces heat. Give one advantage and one disadvantage of this property.
21. Mention three ways in which friction between two surfaces can be minimised.
22. Mention three examples by which friction between two surfaces can be increased.
23. State and explain different types of friction.
24. Define(a) Fluid friction.(b)Streamlining.
25. What are the advantages of frictional force in our daily life?
26. Define force of friction .How is the force of friction disadvantageous ?
27. Mention three disadvantages of friction between the parts of a machine. How does (a) oiling and (b) using ball bearings help reduce friction.
28. Why a cycle slows down when we apply brakes?
29. Define static and sliding friction.
30. Why it is easier to move a box, which is already in motion than to get it in motion?
31. You spill some soapy water on the floor. Would it make it easier or more difficult for you to walk on the floor? Explain.
32. State rolling friction is smaller or greater than sliding friction.
33. Explain why sportsmen use shoes with spikes.
34. Explain why it is hard to drag a mat when a person is sitting on it than no one is sitting on it?
35. Define lubricant. Give some examples.
36. Can friction be reduced to zero by polishing or excessive use of lubricants?
37. State the factors on which fluid friction depends.
38. Why kabaddi players rub their hands with soil?
39. Explain why objects moving in fluids must have special shapes.
40. Fill in the blanks with proper words.  (a) Friction opposes the------- between the surfaces in contact with each other. (b) Friction occurs due to the------ between the two surfaces.(c)Sliding friction is ------ than the static friction.