# Speed of Force or 'Transfer of Momentum'

Discussion in 'Physics & Math' started by hansda, Feb 14, 2013.

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1. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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The water is RECEIVING the E that the person is adding: Ein-Eout= 0

3. ### eramSciengineerValued Senior Member

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I explained this in #253. You must have short term memory loss.

Genius.

5. ### hansdaValued Senior Member

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If the person(swimmer) is adding(losing) energy E and water is RECEIVING the E; then how the swimmer(person) is moving forward due to "Reaction-Force" as explained in the example?

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8. ### eramSciengineerValued Senior Member

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I am NOT kidding, you really appear to have short term memory loss.

9. ### originTrump is the best argument against a democracy.Valued Senior Member

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The person is converting some of the chemcial potential enegy of their body into kentic energy but a large percentage of the converted potential energy is lost to friction which is putting energy into the water. If the person stops swiming the water friction will stop the person and then all of the energy will go to the water from friction.

10. ### hansdaValued Senior Member

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Your post #253 is incomplete and wrong. If you compare your post with the example of the swimmer, you have only explained action-force of the swimmer. You remain completely silent about the reaction-force.

In other words, your idea of "reaction-force" and the "reaction-force" as explained in the example of swimmer are not matching.

11. ### hansdaValued Senior Member

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What you explained here is basically "transfer of energy from the swimmer to the water". This is "action-force" of the swimmer to the water. As per the example the swimmer does not move due to "action-force".

The swimmer moves due to "reaction-force". So, what about "reaction-force"? How energy transfer is happening in "reaction-force" ?

12. ### originTrump is the best argument against a democracy.Valued Senior Member

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What exactly is your question? The swimmer pushes against the water and the reaction force is the water pushing against the swimmmer.

13. ### hansdaValued Senior Member

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My main question here is: whether action-force and reaction-force as explained in the example are simultaneous or not?

In other words, whether the "energy transfer in action-force(from the swimmer to the water)" and the "energy transfer in reaction-force(from the water to the swimmer)" are simultaneous or not?

This is right. So, in the reaction-force some energy transfer is happening from the water to the swimmer.

14. ### eramSciengineerValued Senior Member

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This was my post: (#253)

which I said applies to your question:

I didn't even use the term "action-force". So I have no idea what you're talking about.

15. ### eramSciengineerValued Senior Member

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Yes they are simultaneous.

from the swimmer's glycogen to the swimmer's body and the water.

16. ### hansdaValued Senior Member

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I already told you your post #253 does not match with the example of the swimmer. Your post #253 does not apply completely to my post #254.

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18. ### hansdaValued Senior Member

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If both the energy transfers(from the swimmer to water(E) and from water to swimmer(E)) are simultaneous, then we are having a total energy 2E in the system due to input energy E (which is done by the swimmer to the water).

So, where is the conservation of energy?

19. ### hansdaValued Senior Member

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In your post#253, you only considered energy transfer from ball A to ball B. You did not consider energy transfer from ball B to ball A.

In the swimming example, the "swimmer" can be compared with "ball A" and the 'water' can be compared with 'ball B'.

20. ### eramSciengineerValued Senior Member

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There's a net energy transfer from A to B.

21. ### originTrump is the best argument against a democracy.Valued Senior Member

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The water does not transfer energy to the swimmer. Let's just look at an arm moving through the water. The arm has kenetic energy. The movement puts a force on the water there some reactive force of the water. It is rather complicated since the water is a liquid so the water moves out of the way of the moving arm, but there is some reactive force. This result in a net force on you shoulder.

Why do you always try to make things more difficult?

edit: Removed the part refering to normal force - didn't want hansda off on another tangent.

Last edited: Apr 2, 2013
22. ### Russ_WattersNot a Trump supporter...Valued Senior Member

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You keep saying that wrong: there is only one energy transfer and it is from swimmer to water.

23. ### hansdaValued Senior Member

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Can you clarify about action-reaction pair in your following example? I will give you two options. Choose one of these two options for action-reaction pair.

Option-1) Object B gaining energy is ACTION and object A losing the same energy is REACTION.

Option-2) Energy transfer from object A to object B is ACTION and the energy transfer from object B to object A is REACTION.

Which option is true? Option-1 or Option-2.