How Much Force is Needed to Climb a Hill at Constant Speed with Air Resistance?

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Homework Help Overview

The problem involves a bicyclist of mass 68.0 kg coasting down a 6.90 degree hill at a steady speed of 5.80 km/hr due to air resistance. The question is how much force is needed to climb the hill at the same speed while accounting for the same air resistance.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the application of free body diagrams (FBD) and the summation of forces in both x and y directions. There is a question regarding the value of acceleration when moving at a steady speed.

Discussion Status

Some participants suggest using the downhill scenario to deduce the magnitude of air resistance, while others express confusion about which formula to apply for air resistance. A participant notes that the steady speed indicates a specific condition about the net force acting on the bicyclist.

Contextual Notes

There is a mention of the air resistance equations not being applicable, and participants are exploring the implications of steady speed on net forces.

BMWPower06
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Homework Statement


If a bicyclist of mass 68.0 kg (including the bicycle) can coast down a 6.90 degree hill at a steady speed of 5.80 km/hr because of air resistance, how much force must be applied to climb the hill at the same speed (and the same air resistance)?


Homework Equations


The air resistance equations don't seem to apply.

F=MA as always


The Attempt at a Solution


I drew the FBD, tried to sum the forces and got:
The sum of forces in x= mgsino-Fa (force of air resistance)= ma
Sum of forces in y= N-mgcoso=0

Can anyone help me out?
Thanks
 
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BMWPower06 said:

Homework Statement


If a bicyclist of mass 68.0 kg (including the bicycle) can coast down a 6.90 degree hill at a steady speed of 5.80 km/hr because of air resistance, how much force must be applied to climb the hill at the same speed (and the same air resistance)?


Homework Equations


The air resistance equations don't seem to apply.

F=MA as always


The Attempt at a Solution


I drew the FBD, tried to sum the forces and got:
The sum of forces in x= mgsino-Fa (force of air resistance)= ma
Sum of forces in y= N-mgcoso=0

Can anyone help me out?
Thanks
What is the value of the acceleration in the x direction along the incline, if the bicyclist is moving at steady speed?
 
Use the data provided in the downhill case to figure out the magnitude of the air resistance. Then apply that to the uphill case.
 
Doc Al said:
Use the data provided in the downhill case to figure out the magnitude of the air resistance. Then apply that to the uphill case.

im confused as to which formula i use for air resistance.
 
You won't calculate the air resistance directly; instead, you'll deduce it from the fact that the bicyclist moves at a steady speed. What does that tell you about the net force on him?
 

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