A 4 kg object moving to the left collides with and sticks to a 3 kg object moving to the right. Which of the following is true of the motion of the combined objects immediately after the collision? (A) They must be moving to the left.
(B) They must be moving to the right.
(C) They must be at rest.
(D) The motion cannot be determined without knowing the speeds of the objects before the collision.

(D) The motion cannot be determined without knowing the speeds of the objects before the collision.

Explanation:

Given;

mass of the object moving to the left, m₁ = 4 kg

mass of the object moving to the right, m₂ = 3 kg

Since the two masses stick together after collision, the collision will be inelastic.

The two masses will move in the direction of the mass with greater momentum.

Momentum is the product of mass and velocity (mv).

Thus, the direction of the two masses immediately after collision cannot be determined without knowing the speeds of the objects before the collision.