How do you find the necessary height to drop an object to achieve a required impact force?

Question

How do you find the necessary height to drop an object to achieve a required impact force?

Answer 1

There's more to it than just the height.  The force of impact is given by:

F = mv/t

where:

m = mass of impactor

v = speed at time of impact

t = time it takes for impactor to slow down from "v" to zero speed.

Of those 3 variables, only "v" is a function of height (using the formula: v = sqrt(2gh)).  The variable "m" depends on exactly what you're dropping; and the variable "t" depends on not only "v" and "m" but also on the nature of the surface where the impactor hits.  To put it another way: the impact force of hitting a pillow is less than the impact force of hitting concrete, precisely because hitting the pillow increases the value of "t".