Average Force Problem

1. Jan 6, 2004

Forgo

Helping my daughter with her homework (trying to help).
A 65 kg parachuter hits the beach with a speed of 4.0 m/s, making a 0.2 m deep indentation in the sand. With what average force did the parachuter hit the sand?

From what I found in the text it seems you need a time (which they don't provide). How about some clues?

2. Jan 6, 2004

Jimmy

You should be able to calculate the average acceleration that the parachuter experienced as he moved through the .2M of sand. The change in velocity was -4.0 m/s through that .2m of sand. From there the average force should be easily calculated given the mass of the parachuter. I wouldn't think knowing the time is absolutely necessary but there is always more than one way to solve a problem.

Hope this helps.

3. Jan 6, 2004

Jimmy

If you wanted to calculate the time first and then work from there,

$$t = \frac{2 D}{V}$$

Then you can calculate the acceleration from the velocity and time and then the force from there.

4. Jan 6, 2004

Jimmy

I hope what I posted is helping you solve your problem. I have to leave now but if you are still having difficulty, just post where you are stuck and someone will help out.

Good luck.

5. Jan 6, 2004

Forgo

Thanks a lot for the help, we solved the problem just now.

6. Jan 6, 2004

Mathechyst

My two cents:

$$\frac{1}{2}mv^2=Fd$$

Doug

7. Jan 6, 2004

Jimmy

That's a great solution which I also considered but since Forgo mentioned time I thought maybe I should stick with calculating the acceleration. I should have asked what his daughter was actually studying in relation to that problem.