If the distance `s` travelled by a particle in time `t` is `s=a sin t +b cos 2t`, then the acceleration at `t=0` is

Options

A. `a`
B. `-a`
C. `4b`
D. `-4b`

Answer

D

Explanation

Given `s=a sin t+b cos 2t`
`:.(ds)/(dt)=a cos t-2b sin 2t `
`:. (d^(2)s)/(dt^(2))=-a sin t-4b cos 2t`
At `t=0, (d^(2)s)/(dt^(2))=-a sin 0-4b cos 0 =-4b`