incorrect calculator?

[westerndragon76]

I believe that this calculator generates answers assuming that the only force acting on a falling object after it has encountered a stopping surface is the force of the stopping surface. The calculator needs to factor in gravity throughout the whole fall. Would someone else please verify?
http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
Click Mechanics, work-energy principle, and then impact force of falling object, and "Since you know velocity, mass, and kinetic energy, can you predict the force of impact?"
Example numbers:
m=50kg, h=10m, d=5m
stopping force should be about 1480N, but the calculator is saying 980N.

[Gokul43201]

Read the little note at the bottom of that page.

Note that the above calculation of impact force is accurate only if the height h includes the stopping distance, since the process of penetration is further decreasing its gravitational potential energy.

That should take care of your problem (you probably should use d=5, h=5 to describe the situation I think you have in mind). If not for this disclaimer, the calculation would be, as you point out, wrong for the general case where d is not necessarily small compared to h.

[westerndragon76]

I didn't take time to read that disclaimer carefully. Thanks for the quick answer!

[arildno]

It is not a disclaimer, it is a caveat. :mad: