Calculating Power Use on a Hill with Air Resistance and Friction

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The discussion revolves around calculating the power required for a person to ascend an 8-degree hill at a speed of 12 km/h, with a total mass of 75 kg and considering air resistance and friction at 5% of mg. The initial calculation yielded an incorrect power output of 120W, while the expected answer is 0.46kW. Participants suggest using the "force" method for the calculation, emphasizing that both energy and force methods should yield the same result. The original poster expresses anxiety about the problem but feels reassured after receiving guidance. The conversation highlights the importance of method selection in physics problems.
Simonpe
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Hi!

I have a big problem with this simple question. I can manage all the other questions on the paper i got except this one, and it's even one of the easier in there. So please gimme suggestions of what formulas to use:

A person is struggeling his way up a 8 degree hill with the velocity of 12km/h. Calculate the power use. The total mass of him and his bicycle is 75kg. Air resistance and friction is 5,0% of mg.

I tried calculating it with both force laws and energy laws and i end up with the answer 120W (or something i can't remember) but the correct answer should be 0,46kW

Please excuse my bad english, and thanks for the help!

Simon
 
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Show us how you got your answer and we'll give you a hand.
 
Thanks!

Unfortunately I've erased the first soultion and I've only got a lot of unreadable panic notes left :P but can u at least tell me what path to use, Energy or Force? Then i think i'll be able to solve it.

Thanks in advance!
 
Both methods should agree. Go ahead and use the "force" method. :smile:
 
I think i'll manage it now, after hours of studying. Got a test tomorrow morning and i got a little scared that i couldn't accomplish a simple task like that. Btw i used the energy method but thanks for the advice :D

take care and good night
 

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