# Energy/Work Question

## Homework Statement

A skier of mass 67 kg is pulled up a slope by a motor-driven cable.
(a) How much work is required to pull him 40 m up a 30° slope (assumed frictionless) at a constant speed of 1.7 m/s?

m= 67kg
Delta y= 40m
Theta= 30 degrees
v= 1.7m/s

## Homework Equations

I know that:

F=ma
W= F cos(Theta) (Delta y)

## The Attempt at a Solution

I am solving for the force:
F=ma
F= 67 (1.7)
F= 113.9 N/m

With F solved I use my Work Equation:
W= F cos(Theta)(Delta y)
W= 113.9 (cos30) (40)
W= 3945.61 J
W= 3900 J

So you know that he has to be pulled up a distance of 40*sin(30). Work is the force times the component of the directional change projected onto the force (i.e. $F \cdot \Delta s$). Where does this lead you? (Hint: your directional thinking is wrong.)