# The ballistic pendulum

1. May 9, 2007

### leykis101

i did a lab, the ballistic pendulum, and need help with one of the questions in the lab. here it is:
The initial kinetic energy of the projectile is (mv^2/2). The final potential energy of the system is (M+m)gh. However these two values are not equal in this experiment. Explain what happened to the missing energy and why it doesnt really affect the results.
m=the mass of the ball
M=the mass of the pendulum
any help? thanks

2. May 9, 2007

### Staff: Mentor

What do you think? Hint: What kind of collision does the projectile undergo?

3. May 9, 2007

### leykis101

if i had to take an educated guess i would have to say that energy is lost to heat when the ball is embedded into the pendulum. because of this the energy at the top is less than the energy at the bottom. Im not sure if this is correct though.

4. May 9, 2007

### Staff: Mentor

Completely correct! The ball and pendulum undergo an inelastic collision, which transforms some of the ball's original KE into thermal energy.

OK, so why doesn't this "loss" of energy affect your results?

5. May 9, 2007

### Hootenanny

Staff Emeritus
Indeed, that is correct. So that would make this collision an # collision. You could also perhaps mention air resistance, although it is most probably negligable. So why wouldn't this loss of energy affect your experiment?

Edit: The Doc strikes again...

6. May 9, 2007

### DAKONG

the energy conservation formula refer in ideal
why you test many times?... because there are manythings in reality
such as force againts the wind or rusty of metal

yes :!!) maybe sound and heat

Last edited: May 9, 2007