Question

If the external force acting on a system have zero resultant, the centre of mass
(a) must not move
(b) must not accelerate
(c) may move
(d) may accelerate.

Answer 1

Answer:

must not accelerate

Explanation:

(F)ext = m(a)com

(a)com= 0

particle can move with uniform velocity but will have zero acceleration

Answer 2

(b) must not accelerate

(c) may move

Explanation:

• If the external force acting on a device ends in zero, the overall momentum will remain. I.e. conserved constant.
• The center of mass therefore stays at rest or moves at a constant velocity.
• There will be no acceleration if there is no / zero resulting force acting on a system.
• So (b), and not (d).  If it moves with uniform velocity already, it The motion will proceed without acceleration. Therefore (c), and not (a).
• If the external force acting on a system have zero resultant, the center of mas must not accelerate or may accelerate