Average Force Problem

[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?

[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.

[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.

[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. [:)]

[Forgo]

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

[Mathechyst]

My two cents:

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

Doug

[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.