# Homework Help: Kinetic energy of 2 cart system

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1. Oct 20, 2015

### Axel7

1. The problem statement, all variables and given/known data
On cart with a mass of 371 kg and another cart with a mass of 495 kg are rolling toward each other. Just before they collide, the 495 kg cart has a speed of 2.09 m/s, and the 371 kg cart has a speed of 1.90 m/s. We will consider the friction between the cart wheels and track negligible for this problem. Evaluate the translational kinetic energy and convertible kinetic energy of the two-cart system before they collide.
2. Relevant equations
K=1/2mv^2

3. The attempt at a solution
Do you find the kinetic energy for both of the carts? or average the speeds? Also whats the different between translational kinetic energy and convertible kinetic energy

2. Oct 20, 2015

### Staff: Mentor

The total translational KE of a system is the sum of the KE's of all its moving parts.

Now consider a scenario in which there is a two-body collision. Even if the collision is perfectly inelastic it is not always possible to convert all the KE into some other form of energy (like heat or sound or potential energy). This is because conservation of momentum will dictate what the final velocity of the combined object will be post-collision. If there's motion remaining then there's KE remaining, too. So that portion of the original KE could not be converted.

3. Oct 20, 2015

### Axel7

Thank you so much! This helps a lot!