1) The distance moved by the particle in time t is given by s=t3−12t2+6t+8 . At the instant , when its acceleration is zero the velocity is A) 42 B) -42 C) 48 D) -48 Answer: Option BExplanation:s=t3−12t2+6t+8 dsdt=3t2−24t+6 d2sd2t=6t−24 Acceleration =0 ⇒ 6t-24=0 ∴ t=4 Required velocity = dsdt]t=4 =3×(4)2−24×4+6 =48-96+6=42 units