Physics behind Newton's Cradle

  • Thread starter litaa_95
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  • #1
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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?
 

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  • #2
haruspex
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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.
 
  • #3
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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.
 
  • #4
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why would two balls be only half the energy?
 
  • #5
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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?
 
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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.
 
  • #7
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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 :wink:
 

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