Originally Posted by OldCoot
And the correct answers are "Newton's Cradle" and Newton's 3rd Law.
Hate to be finicky, But this does not prove or demonstrate newtons 3rd law. This device, known as a "newtons cradle" illustrates the law of "conservation of momentum", which states:
For a collision occurring between object 1 and object 2 in an isolated system, the total momentum of the two objects before the collision is equal to the total momentum of the two objects after the collision. That is, the momentum lost by object 1 is equal to the momentum gained by object 2.
While its sure that Newton knew of the law conservation of momentum, it is not classically described as one of his 3 laws.
A better illustration of Newtons 3rd law is the recoil you feel when you fire a gun.
P.S. Forgive me, but inside of every engineer is a teacher dying to get out.