Question

The force of a moving object is called momentum. The momentum of an object is proportional to its weight and speed. The more momentum it has, the more force it has. So if there were two cars, both the same model, and one of the cars was traveling 30 mph faster than the other, which car has more force?
(A) The slower car
(B) The faster car
(C) Both cars have equal force
(D) None of the above

Answer 1

The force that a moving object exerts on another object upon colliding with it is rather the change in momentum divided by the amount of time elapsed during the collision.

F = Δp/Δt

F = force, Δp = change in momentum, Δt = elapsed time

Usually we say momentum is proportional to mass instead of saying momentum is proportional to weight. But sure, for two objects on the same planet, greater weight implies greater mass. Momentum is the product of mass and velocity:

p = mv

p = momentum, m = mass, v = velocity

So we have two identical cars on the same planet with one car traveling 30mph faster than the other. Let's say they both collide with a tree, both coming to a rest, and the collisions take the same amount of time to happen. The faster car loses a greater amount of momentum over the same amount of time, therefore delivering a greater force.

Choice B