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

[Chuck 86]

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

 

[Donaldos]

Can't you think of a general expression for work that you could use here?

 

[Chuck 86]

Not of the outside forces

 

[Chuck 86]

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

 

[Donaldos]

What are the outside forces?

In particular, what is the work done by gravity?

 

[Chuck 86]

MgH=(48.7)(9.8)(14)

 

[Donaldos]

OK but H=2.37 m here, not 14m.

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