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Old 28th February 2010, 12:14 AM   #120
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Originally Posted by Tony Szamboti View Post
You are wrong.

If the deceleration is just g then the force is F = mg and the same as the static load. To get an amplification to twice the static load you need F = m x 2g.

It sounds like you are confused about what is happening at rest. Why is the static load equal to mg?
Uh, no, YOU are wrong. Have you ever drawn free body diagrams? This is not that complex an item.

Down is mg, call the force up N. Call up positive and down negative.

If there is no deceleration, then sum of forces = 0. So -mg+N=0, and N = mg.

If there is a deceleration it must be UPWARDS deceleration (because downwards g makes things go faster not slow down). So -mg+N=ma, and

N = ma + mg.

Therefore, if a = g, then N = 2(mg)

which is twice static load.

Don't tell me I'm wrong, Tony. I teach this stuff.

If you ignore this, I will take it as recognition that you were previously incorrect.

Last edited by sylvan8798; 28th February 2010 at 12:16 AM.
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