Question

A particle moves along a straight line such that its displacement at any time t is given by s = (t³-6t²+3t+4) metres. The velocity when the acceleration is zero is

(a) 3 m/s

(b) 42 m/s

(c) -9 m/s

(d) -15 m/s.

Answer 1

Correct option (c) -9 m/s

Explanation:

Displacement (s) = t³-6t²+3t+4 metres.

velocity (v) = ds/dt = 3t²-12t+3

acceleration (a) =  dv/dt = 6t-12.

When a = 0, we get t = 2 seconds.

Therefore velocity when the acceleration is zero (v)

= 3 x (2)² - (12 x 2) + 3 = - 9 m/s.