# Calculate KE of Projectile after Passing through Object.

1. Jan 22, 2012

### PotatoSmasher

Hi I am new to the forums and currently studying year 12 physics. I was wondering is it possible to calculate the Kinetic Energy lost from a projectile, say a bullet, after passing through an object, say a piece of steel. I know the weight of the bullet (41.9g) and it's initial KE (17,820J). I also know the density of the steel (7.85 g/cc) and its thickness (5mm).

Note please this isn't a homework question, it's just for my own curiosity and expansion of my own knowledge. Many thanks :)

2. Jan 22, 2012

### tiny-tim

Welcome to PF!

HI PotatoSmasher! Welcome to PF!

No, there's too many variables …

it depends on the shape of the bullet, amongst other things …

if you were in CSI, you'd find the answer by actually firing bullets at a sample of the metal

that's really the only way

3. Jan 23, 2012

### sophiecentaur

These are fun.

4. Jan 23, 2012

### PaulS1950

All you need to do is measure the velocity of the projectile after it passes through the material and get its mass after you measure the velocity. Then it is Ek=1/2 MxV^2.
Paul