Newtons Third Law , Impulse and momentum

Newton Three is

F1,2 = - F2,1

Reads the Force of Body 1 on Body 2 is the negative of Body 2 on body 1

A collision occurs over a time t, during which the two bodies are touching, and if elastic the surface is compressing and then throwing the objects apart.

N3 x t gives

F1,2 x t = - F2,1 x t

Reads the impulse (Symbol 'I') of body 1 on body 2 is the negative of body 2 on body 1

Impulse is defined F x t, and has units Newtons Second or Ns remember that t is the contact time.

This has a number of consequences,

ONE: You can design cars to have lower force collisions over longer times,

TWO: the momentum of a system does not change in a collision

Consider two collisionsOne over a short time,Two with a crumple zone over A long time with a force less than the lethal force.

Unfiled Notes Page 1