(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Sam, whose mass is 75 kg, straps on his skis and starts down a 50-m-high, 20 degree frictionless slope. A strong headwind exerts a horizontal force of 200 N on him as he skies.

Find his speed at the bottom of the slope using Newton's Law

Find his speed at the bottom of the slope using Energy

2. Relevant equations

Conservation of Energy

F = ma

vf^2 = vi^2 + 2ad

ME_i = ME_f

3. The attempt at a solution

I set up a drawing, found the length of the slope, did the force analysis, and got the following (Newton's Laws part):

Length of the slope = 146.19m

Force down the slope = m*g*sin(20) = 251.3848N

Force of wind up the slope = 200/cos(20) = 212.835

So Fnet = 251.3848-212.835= 38.549

a = Fnet/m = 38.549/75 = .5139

Kinematics:

vf*vf = vi*vi + 2(a)(d)

vf*vf = 0 + 2(.5139)(146.19)

vf = sqrt(150.28) = 12.25 m/s

Not sure where I went wrong.

As for the energy part, I'm not sure how to approach it.

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# Homework Help: Energy vs. Newton's Laws

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