Question

A nonzero external force acts on a system of particles. The velocity and the acceleration of the centre of mass are found to be v0 and a0 at instant t. It is possible that
(a) v0 = 0, a0 = 0
(b) v0 = 0, a0 ≠ 0
(c) v0 ≠ 0, a0 = 0
(d) v0 ≠ 0, a0 ≠ 0

Answer 1

Answer:

option (d)

since it's a nonzero external force ,then it must be option (d)

Answer 2

(b) $v_0$ = 0, $a_0$ ≠ 0

(d) $v_0$ ≠ 0, $a_0$ ≠ 0

Explanation:

• The system will not only rotate around the central axis, even if the net external force provides torque.

• But according to the second law of Newton, the center of mass will also be accelerated in the direction of force.
• And (a) it can be a true declaration.
• If the central axis of the device is however fixed, The system will only rotate, but its center mass will not accelerate in the direction of motion.
• Here the force provided by the thing used to hold the central axis set will have to provide a counter-force to stop Center Mass's acceleration.
• A non zero external force acts on a system of particles where the velocity and the acceleration of the center of mass are found to be $v_0$ and $a_0$. For this condition the possibilities are  $v_0$ = 0, $a_0$ ≠ 0 and

$v_0$ ≠ 0, $a_0$ ≠ 0