Motion of COM — Practice Quiz

Question 1

A bomb of mass 5 kg moving at 4 m/s explodes into 3 fragments. COM velocity afterward:

Accepted Answer

4 m/s (unchanged)

Answer

Zero

Answer

Depends on fragment masses

Answer

Cannot determine

Question 2

Two particles of mass 1 kg and 3 kg are at rest. A force of 4 N is applied to the 1-kg particle for 2 s. COM velocity:

Accepted Answer

2 m/s

Answer

8 m/s

Answer

4 m/s

Answer

1 m/s

Question 3

Earth-Moon system's COM lies:

Accepted Answer

Inside Earth (about 4700 km from center)

Answer

At the Earth's center

Answer

Just outside Earth

Answer

On the Moon

Question 4

A projectile of mass 4 kg breaks into two pieces of 1 kg and 3 kg at the highest point. The 3-kg piece falls vertically down. COM of fragments still:

Accepted Answer

Follows the original projectile path

Answer

Falls vertically

Answer

Stops

Answer

Moves opposite to projectile

Question 5

Internal forces in a system:

Accepted Answer

Change individual velocities but not V_COM

Answer

Change V_COM

Answer

Have no effect at all

Answer

Always equal external forces