Related Resources: calculators

Impact Force Formulae and Calculator

Strength Mechanics of Materials

Impact Force of a Blow Formulae and Calculator

Impact force of a blow: A body that weighs W pounds and falls S feet from an initial position of rest is capable of doing WS foot-pounds of work. The work performed during its fall may, for example, be necessary to drive a pile a distance d into the ground. Neglecting losses in the form of dissipated heat and strain energy, the work done in driving the pile is equal to the product of the impact force acting on the pile and the distance d which the pile is driven Since the impact force is not accurately known, an average value, called the “average force of the blow,” may be assumed. Equating the work done on the impact pile and the work done by the falling body, which in this case is a pile driver:


Fave = [ W · ( S + d ) ] / d


Fave = Average force of impact blow (lbf, N),
S = Height (ft, m) through which the driver falls,
d = Distance (ft, m) that the impact pile is driven,
W = Weight / Mass of driver (lbs, grams),
d = Distance (ft, m) which pile mass is driven.


Machinerys Handbook, 30th Edition