Calculating Power Use on a Hill with Air Resistance and Friction

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Homework Help Overview

The problem involves calculating the power used by a person riding a bicycle up an 8-degree hill at a speed of 12 km/h, considering air resistance and friction. The total mass of the person and the bicycle is given as 75 kg, with air resistance and friction accounting for 5% of the gravitational force.

Discussion Character

  • Exploratory, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to use both force laws and energy laws to solve the problem but is unsure of the correct approach. Some participants suggest focusing on the "force" method, while others inquire about the appropriate path to take between energy and force methods.

Discussion Status

The discussion is ongoing, with the original poster expressing some confusion and seeking guidance on which method to use. There is an indication that participants are providing support and suggestions, but no consensus has been reached regarding the best approach.

Contextual Notes

The original poster mentions having erased their initial solution and only having unclear notes left, which may impact their ability to articulate their reasoning fully. There is a sense of urgency due to an upcoming test.

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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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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