Mechanical energy and momentum conservation

Thread starter yolo123
Start date Apr 21, 2014
Tags

Conservation Energy Mechanical Mechanical energy Momentum Momentum conservation

AI Thread Summary

Mechanical energy is not always conserved when momentum is conserved, as demonstrated by inelastic collisions where momentum remains constant but kinetic energy is lost. The presence of external forces affects mechanical energy, but inelastic collisions show that momentum can be conserved without mechanical energy conservation. The confusion arises because both concepts are related but distinct. Thus, the statement that mechanical energy is conserved whenever momentum is conserved is false. Understanding the differences between momentum and mechanical energy is crucial in physics.

Apr 21, 2014

yolo123

Mechanical energy is conserved whenever momentum is conserved. T/F?

My guess is true:
If momentum is conserved, no external forces are applied on the system. Hence mechanical energy can't change! (No change in PE, no change in KE).

BUT: My answer booklet says FALSE! Why?

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Apr 21, 2014

guitarphysics

Momentum is conserved when there's an inelastic collision, but kinetic energy isn't. That's one typical example.

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