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## Homework Statement

a 2.1*10^3 kg car starts from rest at the top of a driveway that is sloped at an angle of 20 with the horizontal. An average friction force of 4.0*10^3 N impedes the car's motion so that the car's speed at the bottom of the driveway is 3.8m/s., What is the length of the driveway?

## Homework Equations

## The Attempt at a Solution

Ff=4000N

2100 Kg

X=20 degrees

Vf=3.8 m/s

Vi=0 m/s

Wnet=1/2MVf^2-1/2MVi^2

Wnet= 1/2*2000*3.8^2

Wnet= 15162 N

Wnet = FfdcosX

15162=4000cos20D

D=4.03m

but the book says 5.1m?

i cant figure out what i did wrong

thx for the help.