Question

A train car with a mass of 1 kg is stuck to another train car with a mass of 2 kg. An Explosion pushes the two carts away from each other. After the recoil, the 1 kg train car is now moving at -2 m/s and we need to find the Velocity of the 2 kg train car.

Answer 1

We know that the momentum is conserved on the system this will mean that:

$p_i=p_f$

where:

$p=mv$

At the beginning the cars are stuck together and we can assume they are at rest; we know that after the explosion the velocity of the 1 kg car is -2 m/s; then we have:

$\begin{gathered} (1+2)(0)=(1)(-2)+2v \\ 0=-2+2v \\ 2v=2 \\ v=\frac{2}{2} \\ v=1 \end{gathered}$

Therefore, the velocity of the 2 kg car is 1 m/s.