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Qedpower
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Homework Statement
A 2.1x10^3 kg car starts from rest at the top of a driveway that is sloped at an angle of 20 degrees with the horizontal. An average friction force of 4x10^3 N impedes the car's motion so that the car's speed at the bottom of the driveway is 3.8 m/s. What is the length of the driveway?
Homework Equations
mass of car =2.1x10^3 kg
velocity (final)=3.8 m/s
average friction force= 4x10^3
driveway sloped at 20 degrees
kinetic energy theorem=1/2m(vf)^2-1/2m(vi)^2
work formula=fd(cos θ)
w=ke
The Attempt at a Solution
If I log the numbers into the kinetic theorem equation
ke=1/2(2.1x10^30)(3.8m/s)^2
If I log the numbers into the work equation
w=4x10^3d(cos 20)
and ke=w
doesn't 4x10^3d(cos 20)=1/2(2.1x10^30)(3.8m/s)^2?
If I simplify this, the distance is 4.03. Is there anything wrong with my equation?