A 2-kg car moving towards the right at 4 m/s collides head on with an 8 kg car moving towards the left at 2 m/s,and they stick together.After the collision,the velocity of the combined bodies is
A)0.
B)0.8 m/s towards the right.
C)0.8 m/s towards the left.
D)2.4 m/s towards the right.
E)2.4 m/s towards the left.

Question

Quizplus · Accepted Answer

We can use conservation of momentum to solve the problem:
initial momentum = final momentum
(2 kg)(4 m/s) + (8 kg)(-2 m/s) = (2 kg + 8 kg)(v)
8 kg m/s - 16 kg m/s = 10 kg v
-8 kg m/s = 10 kg v
v = -0.8 m/s (since the masses stick together after the collision, the velocity is negative to indicate that they are moving to the left)
Therefore, the answer is C, 0.8 m/s towards the left.

A 2-Kg Car Moving Towards the Right at 4 M/s