Discussion
This one got me thinking: if you are hanging from a bar, the load is split into two point loads, totalling your weight.
Does the load increase if you then do a pull-up and if it does, by how much?
I say it doesn't, as there is no other reaction that you can add, as you are already hanging. A mate says it will increase, depending on how hard you pull yourself up (the faster you pull-up, the more the load will increase).
What say you all.
Does the load increase if you then do a pull-up and if it does, by how much?
I say it doesn't, as there is no other reaction that you can add, as you are already hanging. A mate says it will increase, depending on how hard you pull yourself up (the faster you pull-up, the more the load will increase).
What say you all.
tank slapper said:
The load does increase, as you have to overcome your inertia to move. If you are just hanging and not moving, everything is in balance and the downwards force on the bar is just as a result of your weight. In order to make you move upwards though, there has to be an acceleration. In order for there to be an acceleration, there has to be a net upwards force applied to your body. As you are creating this force by pulling on the bar with your arms, that force is applied to the bar and so the total force acting on it is your weight plus the force required to accelerate you upwards.
The faster your pull up the higher the additional force will be since force is directly proportional to acceleration, though it will act for a shorter period. The additional force only acts while your are actually accelerating yourself upwards and will return to just that caused by your weight if you stop at the top and hold the position.
Makes sense - looks like I owe him a beer The faster your pull up the higher the additional force will be since force is directly proportional to acceleration, though it will act for a shorter period. The additional force only acts while your are actually accelerating yourself upwards and will return to just that caused by your weight if you stop at the top and hold the position.
So a fat bloke, who weighs, say 100kg ( ) does a pull-up.
The initial load is 980N (kg x gravity) then the extra load is dependant on how quickly he goes from rest below the bar to rest above the bar (assuming the stop is instantaneous). Pull-up distance is, what, 30cm, lets say he takes 1 second to do it (he's unfit), so acceleration is 0.3 ms-2, making the additional load 100 x 0.3 = 30 kgms-2 (or 30N).
If he does it in half a second (as he gets fitter), then the load goes up to 60N.
Right?
) does a pull-up.The initial load is 980N (kg x gravity) then the extra load is dependant on how quickly he goes from rest below the bar to rest above the bar (assuming the stop is instantaneous). Pull-up distance is, what, 30cm, lets say he takes 1 second to do it (he's unfit), so acceleration is 0.3 ms-2, making the additional load 100 x 0.3 = 30 kgms-2 (or 30N).
If he does it in half a second (as he gets fitter), then the load goes up to 60N.
Right?
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