Explain why friction is necessary to make the disc in Figure roll in the direction indicated.

(a) Give the direction of frictional force at B, and the sense of frictional torque, before perfect rolling begins.

(b) What is the force of friction after perfect rolling begins?

Asked by Abhisek | 1 year ago |  174

#### 1 Answer

##### Solution :-

(a) The frictional force acting on the disc must be opposite to the direction of velocity. Frictional force acts towards left as it opposes the direction of velocity at point B which is towards right .

(b) As force of friction acts in the direction opposite to the velocity at point B, perfect rolling starts only when the force of friction at that point equals zero. This makes the force of friction acting on the disc equal to zero.

Answered by Pragya Singh | 1 year ago

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