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Cfem
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Homework Statement
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
Homework Equations
Conservation of Energy
F = ma
vf^2 = vi^2 + 2ad
ME_i = ME_f
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.