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Work Energy Theorem problem: Dealing with Gravitational Force on a hanging man 
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#1
Apr112, 10:18 PM

P: 18

1. The problem statement, all variables and given/known data
Spiderman, whose mass is 80.0 kg, is dangling on the free end of a 12.0 m long rope, the other end of which is fixed to a tree limb above. By repeatedly bending at the waist, he is able to get the rope in motion, eventually getting it to swing enough that he can reach a ledge when the rope makes a 60.0 degree angle with the vertical. How much work was done by the gravitational force on spiderman in this manuever? 2. Relevant equations Work energy Theorem = (Force)(Displacement) 3. The attempt at a solution So I drew a diagram. I showed that this 80.0 kg spiderman began hanging at 90.0° straight down and then he moved to a 60.0° angle. I showed that the rope was 12 m long. I then set up the formula. A = 90.0° B = 60.0° ∫ (mg)cos(90.0°60.0°) = = (80kg)(9.8m/s)(cos 30.0°) =392 joules 


#2
Apr212, 01:08 AM

HW Helper
Thanks
P: 10,660

How do you calculate work? What force does the Earth exert on Spiderman? What is its displacement? What is the angle between force and displacement? ehild 


#3
Apr212, 01:57 AM

P: 963

Maybe you look at conservation force which is relevant to your case.
http://en.wikipedia.org/wiki/Conservative_force 


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