Q. For a particle moving in a straight line, the displacement of the particle at time $t$ is given by $S = t^{3} - 6t^{2} + 3t + 7$. What is the velocity of the particle when its acceleration is zero?
A) $- 9ms^{- 1}$
B) $- 12ms^{- 1}$
C) 3$\ ms^{- 1}$
D) 42 $ms^{- 1}$
Explanation
(a) $v = 3t^{2} = 12t + 3;a = 6t - 12$
When $a = 0,6t - 12 = 0$
or $6t = 12$ or $t = 2$ s When $t = 2$ s,
$v = 3 \times 2 \times 2 - 12 \times 2 + 3 = - 9ms^{- 1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.