A man sitting in a bosun's chair that dangles from a massless rope, which runs over a massless, frictionless pulley and back down to the man's hand. the combined mass of the man and chair is 103.0 kg. With what force magnitude must the man pull on the rope if he is to rise (a) with a constant velocity)
(c) if the rope on the right extends to the ground and is pulled by a coworker, with what force magnitude must the co-worker pull for the man to rise with constant velocity?
a picture showing the particular case:
f = m*a
The Attempt at a Solution
To find the force magnitude I used newton's second law:
F_res = m * a
where the resulting force being:
T-m*g - T being the cord tension, and since he is rising it is larger than f(g) = m*g
The velocity is constant, and the acceleration is therefore 0, making the equation:
T = (m*g)
but that is not correct, for some reason, which I do not quite understand, the cord tension is 2T, making the actual solution
T = (m*g)/2
In the case where the co-worker is pulling the cord, the cord tension is just T, making the magnitude required to lift the person in the bosun's chair double that of himself lifting.
So while I did get the proper results, I was hoping somebody could shed some light on why one must calculate the cord tension as such i.e. himself pulling equals 2T and just T if somebody else does.
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