Momentum and kinetic energy

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"if kinetic energy of system of particles is zero, then linear momentum of that system of particles is zero but the reverse is not true. That is if linear momentum of a system of particles is zero, then the kinetic energy may not be zero"

This is what I got from my text. Can you provide me with some examples because I am a bit confused. Can you provide some explanation?
Is this true for angular momentum?
 

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  • #2
Vanadium 50
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Consider two particles with mass m, one with velocity +v and one with velocity -v.
 
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  • #3
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Consider two particles with mass m, one with velocity +v and one with velocity -v.
So momentum is zero and kinetic E is not zero. Can you give an example for kinetic energy zero and momentum non zero?
 
  • #4
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So momentum is zero and kinetic E is not zero. Can you give an example for kinetic energy zero and momentum non zero?
KE = sum of 1/2 mv2. Can any of those terms be negative?
Or, imagine covering the whole system with a curtain or box and treating it as one object of total mass M and velocity V.
P=MV, while KE= 1/2MV2+ KE(within system, relative to the center of mass)
If KE = 0, what does that imply? Assume masses are never negative.
 
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