Does Zero Linear Momentum Always Mean Zero Kinetic Energy?

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SUMMARY

The discussion clarifies the relationship between linear momentum and kinetic energy in a system of particles. It establishes that while zero kinetic energy implies zero linear momentum, the reverse is not true; a system can have zero linear momentum while possessing non-zero kinetic energy. The example of two particles with equal mass moving in opposite directions illustrates this principle effectively. Additionally, the conversation touches on the implications of kinetic energy being zero and its relationship to momentum, emphasizing that kinetic energy cannot be negative.

PREREQUISITES
  • Understanding of basic physics concepts, specifically linear momentum and kinetic energy.
  • Familiarity with the equations for kinetic energy (KE = 1/2 mv²) and momentum (P = mv).
  • Knowledge of particle systems and their interactions.
  • Concept of center of mass in physics.
NEXT STEPS
  • Study the implications of conservation laws in physics, focusing on momentum and energy.
  • Explore examples of systems with zero momentum and non-zero kinetic energy, such as particles in motion relative to a center of mass.
  • Investigate angular momentum and its relationship to kinetic energy in rotating systems.
  • Learn about the effects of external forces on momentum and energy in closed systems.
USEFUL FOR

Students of physics, educators teaching mechanics, and anyone interested in the principles of momentum and energy in particle systems.

AdityaDev
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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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Consider two particles with mass m, one with velocity +v and one with velocity -v.
 
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Vanadium 50 said:
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?
 
AdityaDev said:
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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