| A disc is rotating with angular velocity \[(\omega )\] about its axis (without any translation push) on a smooth surface:[AIPMT (M) 2009] |
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A) Find direction and magnitude of velocity at points B and A.
B) Why is friction necessary for rolling?
C) What is direction of friction at point B?
D) None of these
Correct Answer: D
Solution :
[a] In the given case velocity at A, \[{{v}_{A}}=+\omega \left( \frac{R}{2} \right)\] i.e., towards right and velocity at B, \[{{v}_{B}}=-\omega R\] ie, towards left. [b] Friction produces tangential force and torque as per requirement of starting of translation motion and retarding of rotational motion respectively. [c] There is no friction force at point B. [d] The value of friction force is zero in case of perfect rolling on horizontal surface.
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