Physics behind Newton's Cradle

[litaa_95]

So, since the Newtons cradle is all about the conservation of momentum. I was wondering, when one ball is released from one side at a certain velocity, why doesn't two balls at the end swing, at half the original speed?

 

[haruspex]

It's not just conservation of momentum. Most of the energy is conserved too. Two balls at half the speed would only be half the energy.

 

[Infinitum]

The usual steel balls used in the Newtons Cradle are efficiently elastic, meaning they don't lose a lot of energy as heat. This implies most of the energy is conserved. If some other non-elastic material was used, this wouldn't be the case.

 

[litaa_95]

why would two balls be only half the energy?

 

[Infinitum]

why would two balls be only half the energy?

Say the initial single ball of mass m has velocity V, and the two balls each(of mass m) have velocity V/2. Can you find out their kinetic energies and co-relate them?

 

[fermat007]

Then why couldn't the other 4 balls move with velocity V/2? In this case both sides have equal kinetic energy, thereby conserving the energy in the system.

 

[Infinitum]

Then why couldn't the other 4 balls move with velocity V/2? In this case both sides have equal kinetic energy, thereby conserving the energy in the system.

The momentum isn't conserved in this case

 

[rcgldr]

Link to article with good explanation of Neton's cradle:

http://www.lhup.edu/~dsimanek/scenario/cradle.htm

 

[davenn]

Link to article with good explanation of Neton's cradle:

http://www.lhup.edu/~dsimanek/scenario/cradle.htm

Thats brilliant
thanks for the link :)

Dave