Home Alone Paint Cans

I saw a commercial for the classic holiday movie "Home Alone" and wondered about the physics that I saw.  The scene I'm referring to is the one where Macaulay Culkin throws paint cans tied to a rope off of the banister that swing and hit burglars in the head.  

http://www.youtube.com/watch?v=2Lb92tL6R4A

I was interested in the force with which the paint cans hit the robbers.

• I estimated the length of the rope and the mass of the paint can
• L=3m
• mass of paint can=4.5kg
• I found this equation online for the velocity of a pendulum at the bottom of it's swing (aka the point of contact with the robbers' heads)
• v = √{2gL[1-cos(a)]}
• I assumed that the rope didn't get taught until ~45degrees
• v=(2)(9.8m/s^2)(3m)[1-cos(45)]=5.3m/s
• a(radial)=v^2/r
• a(radial)=5.3^2/3m=9.3m/s^2
• F=ma
• F=(4.5kg)(9.3m/s^2)=42N