Friction Worksheet-5

Friction Worksheet-5

31. Give two examples where friction is undesirable.

32. What do you mean by lubricants?

33. Why are oil, creams and grease called lubricants?

34. How are the shoes made to counter the friction and make better grip?

35. What is used in cycle brakes to increase friction?

36. Name the substance which is used in carrom board to reduce friction.

37. What is avoided between two surfaces to make movement smooth?

38. Can we eliminate friction completely?

39. What is used to reduce friction in machines where lubrication are not advisable?

40. Why do pieces of luggage fitted with rollers?

41. Name two methods of reducing friction.

42. How sliding friction is replaced by rolling in machines?

43. Name any machine in which ball bearing is used to reduce friction.

44. What is drag?

45. What are fluids?

46. What does frictional force exerted on an object in a fluid depend on?

47. Name the special shape given to objects moving in fluid.

48. Name some examples which have streamlined body.

49. When does rolling friction come in play?

50. Push the book on a table. You observe that after sometime it stops. Explain why.

Answer:

31. (i) We sprinkle fine powder on carom board to reduce friction.

(ii) Drops of oil are poured on the hinges of a door so that the door moves smoothly.

32. The substances which are used to reduce friction are called lubricants.

33. Oil, creams and grease are called lubricants because they are used to reduce friction.

34. They have grooves on their soles.

35. Brake pads

36. Talcum powder

37. Interlocking of irregularities is avoided.

38. No

39. Air cushion

40. Pieces of luggage fitted with rollers to reduce single friction so that even a child can pull such luggage easily.

41. (i) By rolling, (ii) By sliding

42. By using ball bearings.

43. Ceiling fan

44. The frictional force exerted by fluids is called drag.

45. Commonly gases and liquids are called fluids.

46. Friction depend on the speed with respect to the fluid and the nature of fluid.

47. Streamlined shape.

48. Boats, aeroplanes and ships.

49. When a body rolls on other body then rolling friction come in play?

50. When we push a book on a table then a force acts on the book which opposes its motion.

This force is called force of friction. The friction opposes the movement due to which the book stops.