Posted by **neosha** on Thursday, June 24, 2010 at 12:02am.

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 -
**Quidditch**, Thursday, June 24, 2010 at 12:41am
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 -
**neosha**, Thursday, June 24, 2010 at 1:05am
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 -
**Quidditch**, Thursday, June 24, 2010 at 1:25am
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 -
**Dr Russ**, Thursday, June 24, 2010 at 6:20am
Remember that the answer should be in KJ. I think you mean kJ.

- college physics -
**Quidditch**, Thursday, June 24, 2010 at 10:36am
Yes, thanks!

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