- #1

Jack_Straw

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## Homework Statement

A car of weight 1490 N operating at a rate of 121 kW develops a maximum speed of 49 m/s on a level, horizontal road.

Assuming that the resistive force (due to friction and air resistance) remains constant, what is the car’s maximum speed on an incline of 1 in 20; i.e., if θ is the angle of the incline with the horizontal, sin θ = 1/20? Answer in units of m/s.

## Homework Equations

P=FV

## The Attempt at a Solution

*find force:*

force=power/velocity

F=121,000/49

*find θ:*

θ=sin

^{-1}(1/20)

*find F at angle θ:*

F

_{θ}=(121,000/49)/cos(sin

^{-1}(1/20))=2472.48N

*find F*

_{N}at angle θ:F

_{Nθ}=(1490N)(sin(sin

^{-1}(1/20)=74.5N

*find F*

_{netθ}:F

_{netθ}=F

_{θ}-F

_{Nθ}=2472.48N-74.5N=2397.98

*insert F*

_{netθ}into V=W/F:V=121,000/2397.98=50.46m/s

This answer is reported as wrong. Any ideas? Thanks