- #26

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Read all three of newtons laws

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

What I am saying is a combination of all three of them. Let me just think a little more about to break it down so you see how each one applies in this case.

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- Thread starter tmn50
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- #26

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Read all three of newtons laws

http://en.wikipedia.org/wiki/Newton's_laws_of_motion

What I am saying is a combination of all three of them. Let me just think a little more about to break it down so you see how each one applies in this case.

- #27

Delphi51

Homework Helper

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Have you calculated the force?I wouldn't say that how can a skater's feet stand such a force this sport would have been banned if it was so

I think we agree there is a centripetal acceleration and force for the circular path up to the point C. If you accept the force a nanometer before C, why does it suddenly become so unreasonable to have it for one more infinitesimally small distance?

- #28

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the body started with no speed

and I don't know there is something which make no sense in this when i calculated the force it was 2400 N (nothing wrong ) while mg = 800 N

- #29

Delphi51

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The skater does accelerate downward as if in free fall. However, a nm down the path there is some velocity and a tiny bit of centripetal acceleration to the left. As the skater continues to fall, velocity and centripetal acceleration increase.

Your 2400 N calc is for centripetal force plus gravitational force, right?

I'm finding it interesting that the centripetal force is twice the gravitational force regardless of the height = radius. Since potential energy is converted entirely to kinetic energy as it falls,

PE at top = KE at bottom

mgR = ½mv²

v² = 2gR

Putting this into Fc = mv²/R

gives Fc = 2mg.

The total force pushing up on the skater at the bottom of the path is three times gravity regardless of the radius. Most interesting! Skateboarders are experiencing 2 G's of acceleration but feeling 3 times their normal weight at the bottom of a bowl.

- #30

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thanks man I really apreciate it

- #31

Delphi51

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Most welcome. Quite an interesting problem, too.

- #32

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thanks a lot Delphi51. I don't think would have managed to make it that clear.

- #33

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I don't mean to be a bother but i have a problem with an electrochemical cell

here is the link if you would like to give me a hand

https://www.physicsforums.com/showthread.php?p=3317518#post3317518"

here is the link if you would like to give me a hand

https://www.physicsforums.com/showthread.php?p=3317518#post3317518"

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