Physics Inelastic Collision: Initial Velocities & Kinetic Energy

[onecoolcat]

Can anyone help me with a physics Inelastic Collision question:

A truck mass weighing 3000kg collides into a car that is at rest weighing mass 1000kg. they stick together after the collision and the kinetic energy loss was 100kj=J. The final velocity after the collision is 15 m/s. I need to find out what the initial velocity of the two vehicles were prior to the collision and change in kinetic energy. My teacher show how to find the velocity AFTER the collision but nothing about how to find the velocity PRIOR to the collision. Can anyone help?

 

[Doc Al]

My teacher show how to find the velocity AFTER the collision but nothing about how to find the velocity PRIOR to the collision.

You use a similar method/equation. The only difference is that you'll be solving for a different unknown.

What's conserved during the collision? Set up a conservation equation.