Collisions: does the total momentum change?

Two trolleys move towards each other, collide and stick. You will make the program find the total momentum before, their speed together afterwards, and how much kinetic energy is lost. Then it draws the momentum before and after as bars.

The idea. With no outside force, total momentum before $=$ total momentum after: $m_Au_A + m_Bu_B = (m_A + m_B)\,v$. Kinetic energy $\tfrac12 mv^2$ is not kept when they stick.

Your tasks.

1. Work out p_before, the total momentum before.
2. Work out v, their velocity together after the collision.
3. Work out ke_lost, the kinetic energy before minus after.