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Topic Date User

rope jump 1-May-2007 At 4:44:54 PM TonyB

Message

>force at each point was what i was talking about, which isn't the same
>througout the rope.

The simplest demonstration that force is uniform throughout the rope, is to tie spring balances between lengths of rope, and pull ... all balances will show the same force. Stress in the rope is force divided by cross section area ... this may change if the cross sectional area is not constant.

> if it gets taken up over
>a shorter time the force is higher.
> ... there's a whole lot more energy around

The kinetic energy of the falling body/person is equal to it's (mousey's) initial potential energy, which is proportional to the height he falls (ignoring energy lost in heating the air.) The force in the rope is proportional to the distance the rope stretches, not the time in which it does so. You may recall: Energy = Work = Fs.
We assume the height of the jump is equal to the length of the rope. Since the stretch length is proportional to the length of the rope, the force will be the same for different height jumps, ignoring air resistance. Air resistance will reduce the force for bigger jumps.
Always make sure there is no damage to ropes, no matter what height you are jumping or falling from.