Calculating Average Force on Proton in Metal Film

[dcangulo]

A proton (m=1.67x10^-27 kg) that has a speed of 5.0x10^6 m/s passes through a metal film of thickness 0.010mm and emerges with a speed of 2.0x10^6 m/s. How large an average force opposed its motion through the film??

can anybody give me a clue on where i can start?

 

[Astronuc]

Force, F = mass * acceleration.

There is an equivalence between energy and force applied over distance.

If a mass is accelerated uniformly (at an acceleration a) from velocity v1 to velocity v2 over a distance x, what is the relationship between v1, v2, a and x?