Conversion of KE when a force does not do work

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Discussion Overview

The discussion revolves around the concept of energy conservation in scenarios where a force is applied to an object that does not move. Participants explore the implications of static friction, the role of muscle efficiency, and the nature of forces that do not perform work, such as magnetic forces.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants assert that all energy is conserved, questioning where energy goes when a force is applied without movement.
  • One viewpoint suggests that energy expended in pushing an object that does not move is converted to heat through muscle inefficiency, as the body is not an ideal machine.
  • Another participant introduces the idea that magnetic forces do not do work because they are always perpendicular to velocity, implying that energy remains conserved in such cases.
  • There is a discussion about static friction, with some claiming it converts energy to heat, while others argue that static friction does not dissipate energy, contrasting it with sliding friction.
  • A participant mentions that using a spring to push a stationary object retains all energy within the spring, suggesting a different perspective on energy storage and transfer.

Areas of Agreement / Disagreement

Participants express differing views on the nature of energy conversion when a force does not result in movement. There is no consensus on the role of static friction versus sliding friction, and the discussion remains unresolved regarding the specifics of energy dissipation and conservation in these contexts.

Contextual Notes

Participants highlight various assumptions about energy transfer, the efficiency of human muscles, and the definitions of work and energy in different scenarios. The discussion reflects a range of interpretations and conditions under which energy conservation is considered.

musicboy
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All energy is conserved.
So if I push on an object and it doesn't move, where does that energy go?
 
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That can only happen when you have static friction and in such a situation, the energy is converted to heat through friction and is distributed among different parts of the environment and the object. The whole energy is conserved but not the object's energy.
But when you say a force doesn't do work, it can mean something else too. You may have magnetic forces([itex]q\vec v \times \vec B[/itex]). It does no work because its always perpendicular to velocity. The particle's energy is conserved here.
 
musicboy said:
All energy is conserved.
So if I push on an object and it doesn't move, where does that energy go?

Your body is not a very efficient machine. In this case, all of the energy you expend is used to tighten your muscle fibers, which stretch under the applied force. This means that all of the energy goes into stretching your muscles, eventually turning into heat, and none of it goes into moving the object.
 
musicboy said:
All energy is conserved.
So if I push on an object and it doesn't move, where does that energy go?

What energy?

Simply pushing on a stationary object doesn't give it any energy. It might feel like hard work but that's only for the reason others have given...namely that humans are not ideal machines. We are quite inefficient and consume energy even when not doing useful work. Much of that energy escapes as heat.

If you use a spring to push on the same stationary object you will find no energy leaves the spring. It all stays stored in the spring.
 
Shyan said:
That can only happen when you have static friction and in such a situation, the energy is converted to heat through friction
Static friction is not dissipating energy as heat. Sliding friction is.
 

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