# Homework Help: Pile Driver I-Beam Problem

1. Nov 4, 2008

### sylavel

1. The problem statement, all variables and given/known data
A 2580 kg pile driver is used to drive a steel I-Beam into the ground. The pile driver falls 2.52 m before contacting the beam, and it drives the beam 5.58 cm into the ground before coming to rest.
Find the magnitude of the average force for the beam exerts on the pile driver while the pile driver is brought to rest.

2. Relevant equations
F=ma

3. The attempt at a solution
ok so looking at this problem the first thing that came to my head is that i need to find the proper force and divide in by the 5.58 cm converted to meters to get the magnitude of force.
So i plugged in F=ma F=(2580)9.8
giving me 25284
but im not seeing where the 2.52 meters should come into play.

2. Nov 4, 2008

### mgb_phys

f=ma is correct but acceleration also means slowing down as well as speeding up.
You are looking for the force needed to slow the pile driver from whatever speed it was doing qwhen it hits to zero in a distance of 5.58cm.

3. Nov 4, 2008

### sylavel

okay so i need to take the negative acceleration into play that makes sense.
so do i first need to first the velocity of the pile driver while it is falling 2.52 meters?

4. Nov 4, 2008

Yes and yes