A 2500-N pile-driver ram falls 10 m and drives a post 0.1 m into the ground. The average impact force on the ram is

Question

Quizplus · Accepted Answer

The average impact force can be calculated using the work-energy principle. The work done by the impact force is equal to the change in kinetic energy. Initially, the ram has potential energy (PE = mgh) which is converted into kinetic energy (KE) just before impact. At impact, this energy is used to do work in driving the post into the ground. The work done (W) is equal to the force (F) times the distance (d), so W = Fd. Given that the ram falls 10 m, the potential energy converted into work is PE = mgh = 2500 N * 10 m = 25,000 J. The work done to drive the post 0.1 m into the ground is thus 25,000 J, and since W = Fd, we have 25,000 = F * 0.1 m, solving for F gives F = 250,000 N.

A 2500-N Pile-Driver Ram Falls 10 M and Drives a Post