If this machine was 100% efficient, how much force would it take to lift myself off the ground?

Question

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Use this one:
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Answer 1

Note:, you'd need 10 independent pulleys.

A rope can only transmit tension, not shear, compression, or bending moments. There is a theorem in mechanics related to this fact that states the tension anywhere along a rope in a series of pulleys must be the same. (Note: clearly the tension along a string of beads is not the same, but in a series of pulleys the tension is the same....)

Thus the force in each of the 10 parts of the rope between you and the fixed part of the hoist added together, is equal to your weight. So the tension at the end of the rope that you are holding is 1/10 your weight.

Edit: whoops, I forgot that you're also pulling on the end of the rope, in order for force to be conservative, the tension would have to be 1/11 your weight.....

Answer 2

As you say the rope is wrapped 5 times round the two pulleys, I will suppose that means there are 10 lengths of rope between the two pulleys. So the velocity ratio of the machine will be 1:10 - because for every foot I pull the string, the lower pulley will rise by 1/10 foot. The mechanical advantage (if the machine is 100% efficient) will therefore be 10:1, and the force required would be 200/10 = 20 lb force.

Answer 3

Since the pulley system is wrapped around 5 times, there are 10 ropes that would lift the 200 lbm. And since there is one rope that would pull to lift, that one rope would have to be pulled down at at least 20 lbf.

Answer 4

The force required to lift you off the ground is exactly equal to your weight.

Answer 5

Depends on the weight of the clown nose.

Answer 6

The REAL trick would be for the machine to lift ITSELF off the ground...........