How Much Kinetic Energy Is Lost in a Collision Between Two Toy Cars?

[nsingh947]

hi just wondering how you would solve this problem

A 3 kg toy car with a speed of 6 m/s collides head on with a 2kg car traveling in the opposite direction with a speed of 4 m/s. If the cars are locked together after the collision with a speed of 2 m/s, how much kinetic energy is lost?

 

[rock.freak667]

Find the kinetic energies before impact. Then find the kinetic energy when the two stick together after impact. Find the difference.

 

[danb]

Momentum is conserved, and kinetic energy is easy to calculate for each object. Incidentally, the problem is overspecified. They could have asked you to calculate the final speed from the masses and initial speeds.