Question

Exercises Objective Type Questions Multiple choice questions. on the floor is being pushed from right to left. The force of friction on the box will act A box lying 1. (a) From right to left (b) From left to right (c) In all directions Force that opposes the motion of a body in contact with the surface of another body is (d) Downward (c) Friction (d) None of these Force of friction is a 2 (b) Repulsion (a) Attraction 3. (b) Non-contact force (c) Both (a) Contact force A place where there is no friction is (c) In the air (a) High hills (d) None of these (b) Space (d) Under water 5. Providing wheels on a moving body helps in (a) Increasing friction (b) Decreasing friction () Giving shape to the body (d) None of these Which of the following helps easy motion of a fish in water (b) Angular shape (a) Round shape (c) Streamlined shape (d) Elongated shape 7. Moving bicycle will stop moving when you stop pedaling due to (b) Friction (a) Non-availability of muscular force (d) None of these 6. (C) Lubrication 8 Ball bearings are used to (a) Increase friction (b) Decrease friction (d) Making surfaces smooth (b) A snake (c) Deer (d) Flying bird (c) Add to the area in contact 9. Shape of an airplane has been designed as per the shape of (a) A frog 10. Frictional force increases with the increase in (b) Surface contact area (d) All of these (a) Weight of the object (c) Roughness of the surface 11. Which of the following will show maximum friction? (a) Walking on a rough road with rubber sole shoes (b) A boat being rowed in water (c) A cycle with fiat tyre on the road (d) Rubbing rough side of a sand paper on the rough side of another sand paper 12. Shape of a sharpened pencil to reduce friction resembles the shape of (b) Boat (c) Rocket (d) Airplar (a) Fish​

Answer 1

Answer:

Why do we sprinkle powder on carrom board?

Answer: When powder is sprinkled on carrom board, it smoothens the surface and the stagger moves smoothly. Due to smoothness, the force of friction decreases and stagger moves smoothly.

Q: Why is oil poured on the hinges of door?

Answer: Oil is usually poured on the hinges of door in order to reduce friction so that it can open smoothly. It is due to this that the door works properly without producing any sound or hindrance.

Question: Why are oil and grease applied on moving parts of a machine?

Answer: When oil and grease are applied on the moving parts of a machine, it forms a thin layer and the moving surfaces do not directly rub with each other. So, interlocking can be avoided to great extent. That is the reason oil and grease are recommended for machine.