Physics Momentum

Question

A 3500-kilogram vehicle moving easy at 50 km/h collides head-on with a 6000-kilogram vehicle moving west at 40 km/h. The two vehicles lock together. Which way will the wreckage move, and what is the momentum?

Answer 1

I am assuming that the word "easy" should be "East".

I will consider Eastward direction as positive and Westward direction as negative.

Let

m = 3500 kg be the mass of the Eastward vehicle,

M = 6000 kg be the mass of the Westward vehicle,

v = 50 km/h be the velocity of the Eastward vehicle,

V = -40 km/h be the velocity of the Westward vehicle,

w (to be calculated) be the velocity of the wreckage.

The wreckage will have mass m+M and will have the same momentum as

the two vehicles before the collision.

That is

(m+M)w = mv + MV

So

w = (mv + MV)/(m + M)

Substituting actual numbers

w = (3500×50 + 6000×(-40))/(3500 + 6000) = -6.8 km/h

Since the resulting velocity is negative, the wreckage will move Westward.

The momentum is

mv + MV = -65000 kgkm/h