Max weight that anyone can lift using over head pulley.

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Discussion Overview

The discussion revolves around the mechanics of lifting weights using an overhead pulley system, specifically examining whether a lighter individual (50 kg) can lift a heavier individual (70 kg) through the application of force on the pulley. The scope includes theoretical considerations of force, tension, and the implications of weight and acceleration in a frictionless environment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the lighter man cannot lift the heavier man due to the lack of ground support, implying that his arm strength is irrelevant in this scenario.
  • Another participant argues that if the lighter man pulls harder than 70 kg, both individuals would leave the ground, but maintaining that force is necessary to keep the heavier man aloft.
  • A different viewpoint indicates that if the lighter man pulls with a force between 50 kg and 70 kg, he would ascend the rope without moving the heavier man.
  • It is proposed that the maximum load that can be lifted on the other side of the pulley should be less than the lifter's own weight unless the lighter man is secured to the ground, allowing him to exert more force.
  • One participant clarifies that if the lighter man accelerates upwards, he can exert a downward force greater than his weight, potentially lifting the heavier man.

Areas of Agreement / Disagreement

Participants express differing views on the mechanics of lifting with the pulley, particularly regarding the conditions under which the lighter man can lift the heavier man. No consensus is reached, as some argue for the necessity of ground support while others explore the implications of acceleration.

Contextual Notes

The discussion includes assumptions about the absence of friction at the pulley and the implications of weight and force, which may affect the conclusions drawn by participants.

bazzoo
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Can a man whose weight is 50KG (but powerful arms) lift another man with 70 KG weight using an overhead pulley.

I guess no since the light man is not clamped to the groud, his arm strength will not bear any significance and he can lift only the wieght(on other side of the pulley) equal to his own weight. Please comment.
 
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If the light man pulled harder than 70 kg, both men would leave the ground at the same time, but the only way to keep both men off the ground would be for the light man to keep pulling harder than 70kg and climb up the rope faster (and higher) than the heavy man was lifted.

If the light man stopped climbing, the tension in the rope would reduce to below 70kg and the heavy man would fall back to the ground.

If the light man pulled with between 50kg and 70kg, he would climb the rope and the heavy man would not move.

If there is no friction at the pulley, it doesn't make any difference which man pulls on the rope, provided the tension in the rope is greater than 70 kg.
 
Thanks for the reply..So effectively the man pulling the rope (50 KG) cannot lift the heavier man (70KG). He can just climb the rope at his side. If he doesn't the rope may snap at max due to tension but in no way can the heavy man come above ground.

Hence Can it be assumed that the maximum load anyone can lift on other side of pulley(frictionless) should be less than his own weight despite his powerful arms.


Only way to Lift the heavy man would be to clamp the lighter man to ground somehow and then he can utilize his powerful arms to exert more that 70 KG pull.

Please comment ..
 
bazzoo said:
Please comment ..

That's not what I said. Read it more carefully.
 
bazzoo said:
Thanks for the reply..So effectively the man pulling the rope (50 KG) cannot lift the heavier man (70KG). He can just climb the rope at his side. If he doesn't the rope may snap at max due to tension but in no way can the heavy man come above ground.

If he climbs fast enough, he can lift the heavier guy, as AlephZero said. It's a question of acceleration: if he accelerates up the rope, he can exert a downwards force on it that is greater than his own weight. In this case both men rise, the lighter one faster than the heavier one. So the lighter guy will get to the pulley first.

Hence Can it be assumed that the maximum load anyone can lift on other side of pulley(frictionless) should be less than his own weight despite his powerful arms.

If he wants to keep his feet on the ground, yes. Otherwise see above.

Only way to Lift the heavy man would be to clamp the lighter man to ground somehow and then he can utilize his powerful arms to exert more that 70 KG pull.

That'll work.
 
AlephZero & Michael C ...Thanks a ton..I think this clarifies my doubts. :)
 

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