Calculating Work Done by Friction in a Downhill Race: Conservation of Motion

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SUMMARY

The discussion focuses on calculating the work done by friction for a boy in a wheelchair racing downhill. The boy has a mass of 48.7 kg and experiences a constant frictional force of 41.8 N. The initial speed at the crest of the slope is 1.23 m/s, and the final speed at the bottom is 6.27 m/s. The relevant equations include the conservation of energy principle, specifically Ei - Ef = Wfriction + Woutside forces, and the work done by gravity, calculated using the formula MgH.

PREREQUISITES
  • Understanding of basic physics concepts such as energy conservation and work.
  • Familiarity with the equations of motion and forces, particularly in the context of friction.
  • Knowledge of gravitational force calculations (MgH).
  • Ability to manipulate and solve algebraic equations related to work and energy.
NEXT STEPS
  • Calculate the work done by gravity using the formula MgH with the correct height.
  • Determine the total mechanical energy at the top and bottom of the slope to find the work done by friction.
  • Explore the implications of constant frictional forces on motion in physics.
  • Review the principles of energy conservation in various physical systems.
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and energy conservation, as well as educators looking for practical examples of work and friction in real-world scenarios.

Chuck 86
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Homework Statement


boy in a wheelchair (total mass, 48.7 kg) wins a race with a skateboarder. He has a speed of 1.23 m/s at the crest of a slope 2.37 m high and 14.0 m long. At the bottom of the slope, his speed is 6.27 m/s. If air resistance and rolling resistance can be modeled as a constant frictional force of 41.8 N, calculate the work he did in pushing forward on his wheels during the downhill ride.


Homework Equations


Ei-Ef=Wfriction+Woutside forces

1/2mv^2, mgh

The Attempt at a Solution


cant seem to set this up right. don't know the equations for the 2 work
 
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Can't you think of a general expression for work that you could use here?
 
Not of the outside forces
 
that would be cool to get some help instead of pointing out that I am not smart, that's why I am asking for help
 
What are the outside forces?

In particular, what is the work done by gravity?
 
MgH=(48.7)(9.8)(14)
 
OK but H=2.37 m here, not 14m.

Now you just need to calculate the work done by friction.
 

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