# college physics

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An 80kg man walks down a ramp that makes a 40 degree angle with the horizontal. By how much does his gravitational potential energy change (in kJ) when he walks 15m down the ramp?

• college physics -

gravitational potential energy = mgh
where:
m = mass
g = gravitational acceleration
h = height

So, the change in gravitational potential energy is:
delta p = 80kg * 9.8m/sec^2 * (h1 - h2)m

• college physics -

Thank You but I still do not understand what I should do with the angle as far as finding the height is concerned

• college physics -

OK, the ramp makes a 40 degree angle with the horizontal. A sketch might help visualizing this. If you move 15m down the ramp what is the change in the y direction (the height)? It is 15m * sin(40degrees).
So, the potential energy change is:
=(80kg) * 9.8m/sec^2 * (- 15m * sin(40degrees)). Remember that the answer should be in KJ.

• college physics -

Remember that the answer should be in KJ. I think you mean kJ.

• college physics -

Yes, thanks!

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