Assertion (A) The speed of a body in uniform circular motion is constant.
Reason ( R) In uniform circular motion, the acceleration of the body is constant .

Options

A. Both (A) and ( R) are true and (R ) is the correct explanation of (A).
B. Both ( A) and (R ) are true but ( R) is not the correct explanation of ( A).
C. ( A) is true but ( R) is false .
D. ( A) is false but ( R) is true .

Answer

C

Explanation

(i) Assertion is correct : In uniform circular motion body moves with constant speed . It is magnitude of velocity which is constant .
(ii) Reason is incorrect : In uniform circular motion, direction of acceleration (centripetal ) is always along the centre which keep changing when particle moves . As acceleration is vector quantity and its direction is changing so it can not be constant.