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Friction Worksheet-9

Friction Worksheet-9

 

  1. Can we have surfaces with zero friction?

 

  1. Which surface have more friction - rough or smooth? Why?

 

  1. Would it be possible to walk easily on wet marble floor? Why?

 

  1. Why is it possible to write on rough black board with chalk?

 

  1. A ball is set rolling on the ground. Will it stop by itself ? Why?

 

  1. Why do the soles of shoes wear out?

 

  1. Why are the soles of shoes grooved?

 

  1. Why do we sprinkle talcum powder on the carom board?

 

  1. Why does a mechanic use grease between the moving parts of the cycle?

 

  1. Give two examples where rolling friction is utilized.

 

  1. What is function of ridges on your palm and bottom of your feet?

 

  1. Name the two factors on which the magnitude of frictional force depends.

 

  1. Give two methods by which friction is reduced in the wheels of the car.

 

  1. Why does friction increase if the two surfaces are pressed?

 

  1. Why it is easier to move a box which is already moving than one which is at rest?

 

Answer:

  1. No, the friction can be less in some surfaces, but it can never be zero.

 

  1. Rough surfaces have more friction because they have larger number of irregularities.

 

  1. No, it would not be possible to walk on wet marble floor because there is very less friction between the feet and the floor.

 

  1. The chalk is rubbed on the rough blackboard while writing. In the process soft chalk particles get stuck to the irregularities of rough blackboard surface making the writing visible.

 

  1. The ball will stop after sometime because the force of friction is acting from the opposite direction.

 

  1. The soles of shoes wear out due to the friction between the soles and the ground.

 

  1. Soles of shoes are grooved so as to provide better grip between the shoes and the ground.

 

  1. To reduce the friction.

 

  1. Grease is a lubricant used between the moving parts of the cycle to reduce friction and increase efficiency.

 

  1. Rolling friction is utilized by using ball bearings between the hub and the axle of a ceiling fan and the bicycle.

 

  1. The function of the ridges is to increase the friction.

 

  1. Frictional force depends on

(i) the weight of the body and

(ii) the nature of the surface in contact.

 

  1. (a) The wheels of the car are provided with ball bearings along the axle which reduce the friction.

(b) The tube and tyres are inflated which reduce friction.

 

  1. Since the friction is due to the interlocking of irregularities in the two surfaces which slide with respect to each other, it increases when the two surfaces are pressed harder.

 

  1. When the box starts sliding, the contact points on its surfaces, do not get enough time to lock, into the contact points on the floor. So, the sliding friction is slightly less than static friction.