# Heat with relation to work or energy

1. Sep 13, 2011

### aglo6509

Hello,
I know this seems silly to ask, but how could I figure out how much heat was given off when I know the force of an object hitting another?

2. Sep 13, 2011

### Staff: Mentor

What's important is how much macroscopic kinetic energy is 'lost' in the collision, not the force involved.

3. Sep 13, 2011

### aglo6509

So if I know the KE of the system I can find the heat?

4. Sep 13, 2011

### Staff: Mentor

You need the amount of KE 'lost'. There are many kinds of energy other than 'heat' (random thermal energy), but you may be able to assume that most or all of the energy lost goes to 'heat'.

5. Sep 13, 2011

### aglo6509

So if an object starts from rest 1/2 metre away from the object, I would first find Ug then KE right as it hits the object and assume all the lost energy is released as heat?

6. Sep 13, 2011

### Staff: Mentor

If you drop something and it comes to rest, all the mechanical energy (PE + KE) is lost. Some might go to sound and light, but sooner or later it all becomes random thermal motion somewhere.

Just set the initial PE (measured from the final position) equal to the 'heat' for a good estimate.