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 $