# Calculating heat energy

1. Oct 13, 2005

### dragon513

Calculating heat energy....

Q. #1
A 16 kg object is dropped from a height of 25 m and strikes the ground with a speed of 18 m/s. How much heat energy was produced during the fall?

Choices
A) 0 J
B) 2 600 J
C) 1 300 J
D) 3 900 J

Well,according to my calculation, the average acceleration was about 6.48m/s, which means 3.32N/kg acted as air friction.

And I'm lost from there.

Help will be greatly appreciated!

2. Oct 13, 2005

### Tide

HINT: Energy is conserved! :)

3. Oct 13, 2005

### Pyrrhus

Like Tide said remember

$$\Delta K + \Delta U = W_{friction}$$

4. Oct 13, 2005

### Andrew Mason

You don't have to work out force or average speed. Just use potential energy: mgh.

AM

5. Oct 15, 2005

### dragon513

ouch, I learned that a year ago and I have no idea how can I forget such thing ...Thx!