# Homework Help: Gr11 Percentage of Kinetic Energy

1. Nov 10, 2009

### Du312

The numbers aren't important whereas I just need an approach.
So the question goes like this, Jake slid down a slide at a velocity of X m/s (initial velocity), the slide is Y m tall.

a) how much (%) kinetic energy and gravitational potential energy are there before and after Jake slid down the slide?
b) what feature of the slide caused it to be in this way?

ps. it's not Eg = 100% and Ek = 0% before Jake slid down

thx

Last edited: Nov 10, 2009
2. Nov 10, 2009

### ideasrule

I don't quite understand the question. First, is there friction? Second, if Jake is sliding down, shouldn't gravitational energy be converted to kinetic instead of the other way round?

3. Nov 10, 2009

### Du312

there is no friction, and yes gravitational energy is converted to kinetic, but the question's asking how much (what percentage) of gravitational energy is NOT converted... it is kinda confusing but it is how the teacher worded it

actually, we can ignore it. I'm actually more curious about how you would calculate the the percentage of gravitational and kinetic energy in the first place (obviously it's not simply Eg = 100% and Ek = 0% before Jake slid down)

thank you for your reply and i'll revise the question a bit

4. Nov 11, 2009

### ehild

Jake had x m/s initial velocity , so the initial KE was not zero

The total energy at the beginning E= KE(i) +PE(i).

The problem asks the percentage of both the KE and PE with respect to the total mechanical energy.

ehild