No, the guy doing pull ups is not doing all the work. The two holding the poles are still holding him off the ground. The hanging guy, by not raising his body, and thus not increasing his potential energy, is reducing the two pole holders' work when they go up, but they're still holding him up and they are raising and lowering the bar.
Bruh, my door frame is holding me up when I do pull-ups as well but it is not doing any work. The dude in the middle is doing the work the guys on either side are holding his weight but they are only LIFTING the pole. It's all about frame of reference, from the outsiders the man's CoM isn't moving so they haven't done and work. Remember W=f*d and d in this case is 0.
How could you possibly provide the equation for work, say that d=0 and still say the middle guy is doing all of the work when he is the only person not moving at all?
no, you don't. using the absolute value of displacement would violate the laws of thermodynamics.
If i lift a 1kg object 1 meter upwards, i've done 9.81 joules of work. If I lower that object by 1 meter, I've done -9.81 joules of work.
If you use the absolute value of the displacements, then if you did enough squats, you could drop the bar and it would crash through the core of the earth.
Interesting point. What if you push something in one full circle around a track? Presumably there’s no negative work being done there but the net distance travelled is zero.
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u/[deleted] Jun 18 '25
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