# Homework Help: Kinetic energy transfer problem

1. Jan 20, 2005

### Port

ok i have a problem with a 0.005kg coin that has an initial velocity of 25cm/s that hits a 0.015kg coin that is at rest. atfer the collision the 0.005kg coin has a velocity of -12.5cm/s. What i have to find is the Kinetic energy transferred was. i got the final velocity for the 0.015kg coin which is 12.5cm/s but i don't know how to figure out the amt of kinetic enegy transfer is can someone plz help!

2. Jan 20, 2005

### Sirus

Transferred kinetic energy is that which is gained by the coin that was initially at rest. Therefore, you can use

$$E_{K}=\frac{1}{2}mv^2$$

to find the final kinetic energy of that coin, which, since initial $E_{K}=0$, is the transferred $E_{K}$.

Last edited: Jan 20, 2005
3. Jan 20, 2005

### Port

but when i do that i get 1.172 for an answer but it says in my book that the answer is 1.1x10^-4J???

4. Jan 20, 2005

### Sirus

Take a look at your units...

5. Jul 9, 2010

I have an 8lb sledge hammer, traveling 50 mph hitting an immovable object. The energy created is Ek = 1/2 mv^2. Is the energy transfer to the immovable object the same amount?