- #1

Jim01

- 36

- 0

## Homework Statement

Driving an automobile down a slippery, steep hill, a driver brakes and skids at a constant speed for 10m. If the automobile mass is 1700kg and the angle of the slope of the hill is 25 degrees, how much work does gravity do on the car during the skid? How much work does friction do on the car?

## Homework Equations

ΣF

_{x}= 0

W

_{x}= -mgsinΘ

F

_{f}= ?

F

_{f}- W

_{x}= 0

ΣF

_{y}= 0

W

_{y}= -mgcosΘ

N = mgcosΘ

N - W

_{y}= 0

## The Attempt at a Solution

F

_{f}- W

_{x}= 0

F

_{f}= W

_{x}

F

_{f}= -mgsinΘ

F

_{f}= -(1700kg)(9.81m/s

^{2})sin25°

F

_{f}= -7.06x10

^{3}N

It seems to me that if F

_{f}is -7.06x10

^{3}N then the gravitational pull down the hill would have to be an equal but opposite 7.06x10

^{3}N, but I am unsure about this.

W = F

_{s}cosΘ

W

_{g}= 7.06x10

^{3}N cos25° = 6.4x10

^{3}J

W

_{f}= -7.06x10

^{3}N cos25° = 6.4x10

^{3}J

I know that this is an incorrect answer, however, I am unsure of what to do.