Q. 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
A) 12 m s⁻²
B) 24 m s⁻²
C) zero
D) 6 m s⁻²
Explanation
[Solution from source] v = dx/dt = 12 − 3t², which is zero at t = 2 s. a = dv/dt = −6t = −12 m s⁻² at t = 2 s, so the retardation is 12 m s⁻². Zero is wrong because velocity being zero does not make acceleration zero. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.