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**Work (done by gravity) --- pushing up a ramp**

## Homework Statement

A physics professor is pushed up a ramp inclined upward at an angle 28.0^\circ above the horizontal as he sits in his desk chair that slides on frictionless rollers. The combined mass of the professor and chair is 81.0 kg. He is pushed a distance 2.95 m along the incline by a group of students who together exert a constant horizontal force of 600 N. The professor's speed at the bottom of the ramp is 2.15 m/s.

## Homework Equations

W=Fdcos(theta)

## The Attempt at a Solution

I know that if the force of gravity is perpendicular to the force applied then the work done by gravity is zero.

Since the force applied to the professor and chair is horizontal and the force due to gravity on the prof. and chair is vertical i thought the answer would be 0.

This is wrong though. Any suggestions?

Thank you