Question

The car A has a weight of 4000 lb and is traveling to the right at 3 ft/s. Meanwhile a 2000 lb car B is traveling at 6 ft/s to the left. If the cars crash head-on, and at a time instant during the crash the impact force on A is 900 lb to the left, what is the magnitude and direction of the impact force exerted on B at the instant?
(A) 900 lb to the left
(B) 450 lb to the left
(C) 450 lb to the right
(D) 1800 lb to the left
(E) 900 lb to the right

Answer 1

To solve this problem we should apply Newton's third law for which it is defined that there must be an equal reaction in the opposite direction.

From this law, if Car A generates a force on car B, that car must have opposed a force exactly the same but in the opposite direction. The car A moved to the left and generates a force of 900lb so the magnitude of the force in the car B is also 900lb but to the right (opposite direction to the first car)

The correct option is 900lb to the right.