# Newton's Second Law Problem

## Homework Statement

As part of a safety test, an eighteen wheeler is being shot down a track by a rocket into a solid concrete wall. The truck is fully loaded, for a total weight of 95,000lbs. If the truck hits the wall at 80mph and causes a deformation of .1m in the wall before coming to a halt:

a. Draw two free body diagrams, one of the truck and the other of the wall, during the crash.
b. What is the average acceleration of the truck during the collision?
c. what is the average force on the truck during the collision?

## Homework Equations

SumofF=ma
Vf=Vo+2a(Xf-Xo)
Xf=Xo+Vot+(1/2a)t^2

## The Attempt at a Solution

I drew two free body diagrams: (_ is for formatting purposes)

______^________________________________^
______| Fn(Ground->Truck)________________|Fn(Ground-->Wall)
____Truck-->Fp(Rocket->Truck)___________Wall-->Fp(Truck-->Wall)
______|Fg(Earth->Truck)__________________|Fg(Earth-->Wall
______v________________________________v

I'm having trouble finding the average acceleration and the average force, however. I converted the lbs to kg (95,000lbs to 43091.24kg) and the mph to m/s (80mph to 35.7632m/s). I tried treating it as a 1D problem to find acceleration and wrote a table of variables but did not have enough knowns to finish the equations.

Any suggestions would be greatly appreciated.

haruspex