Q: A point size mass 100 gm is rotated in a vertical circle using a cord of length 20cm. When the string makes an angle 60° with the vertical, the speed of the mass is 1.5m/s. The tangential acceleration of the mass in that position is (in ms-2)
(a) 4.9
(b) 4.9 √2
(c) 4.9 √3
(d) 9.8
Ans: (c)
Taking along the tangent
$ \displaystyle mg sin\theta = m a_t $
$ \displaystyle g sin60 = a_t $