Calculating Power Use on a Hill with Air Resistance and Friction

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In summary, the conversation is about a person who is struggling to solve a question involving calculating power use while riding up a hill. They have tried using both force and energy laws, but have ended up with the incorrect answer. They are seeking help and clarification on which method to use. The conversation ends with the person feeling confident that they will be able to solve the problem after studying and thanking the other person for their advice.
  • #1
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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  • #2
Welcome to PF!

Show us how you got your answer and we'll give you a hand.
 
  • #3
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!
 
  • #4
Both methods should agree. Go ahead and use the "force" method. :smile:
 
  • #5
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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