Math Help Forum: Momentum

A railway truck us travelling at 6ms^-1 along a straight piece of track when it hits an identical truck which is stationary. The two trucks couple together automatically. By modelling the trucks as particles find their common speed after the collision.

how do i work this out? the answer is 3ms^-1

thx!

If we say both Truck have mass M kg. Then the initial momentum is (6M+0M)kgms^-1= 6M kgms^-1

After the collision we have the mass of the whole 'body' = 2M kg

and we'll say the 'body' is travelling at Vms^-1. Therefore momentum after collision = 2MV kgms^-1

As momentum is conserved
we have,

6M = 2MV --> 3=V

V= 3ms^-1.

Now, make sure you understand the working by trying some other examples.

The angular momentum of a particle about an origin is a vector quantity related to rotation, equal to the mass of the particle multiplied by the cross [B]...
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