The motion of a particle along a straight line is described by equation : x= 8 + 12t– t³ where x is in metre and t in second. The retardation of the particle when its velocity becomes zero, is :

Options

(a) 24 ms⁻²
(b) zero
(c) 6ms⁻²
(d) 12 ms⁻²

Correct Answer:

12 ms⁻²

Explanation:

x = 8 + 12t – t³ The final velocity of the particle will be zero, because it retarded.
V= 0 + 12 – 3t² = 0 ⇒ 3t² = 12 ⇒ t = 2 sec
Now the retardation a = dv/ dt = 0 – 6t
a [ t= 2] = – 12 m/s²
retardation = 12 m/s²