# Homework Help: Physics help?

1. Jan 11, 2009

### roxxyroxx

Physics help???

1. The problem statement, all variables and given/known data

a child with a mass m slides down a 4.0 m high slide. starting from rest, the child has a speed of 3.5 m/s at the bottom of the slide. what percent of the gravitational potential energy of the child at the top of the slide hasn't been transformed into kinetic energy once the child reaches the bottom?

2. Relevant equations

Ee = 0.5kx^2
Ek = 0.5mv^2

3. The attempt at a solution

idk where 2 start?

2. Jan 11, 2009

### rock.freak667

Re: Physics help???

Since the child is at a distance above the ground, you should use gravitational potential energy instead of Ee (Elastic potential energy)

Find the kinetic energy of the child at the bottom and then find the gravitational pe at the top of the slide.

3. Jan 11, 2009

### roxxyroxx

Re: Physics help???

Ek = 6.1(mass)
Ep = 39.2 (mass)
now...

4. Jan 11, 2009

### NBAJam100

Re: Physics help???

I didnt check the numbers, im assuming they are right. So you have the potential energy, and the final kinetic energy. You want to find what percent of the gravitational potential energy of the child at the top of the slide hasn't been transformed into kinetic energy once the child reaches the bottom. So you can see that there was just more potential energy than kinetic energy, so there is a difference there.

So to find the % of Gpe that hasnt been transformed just subtract the 2 to get the amount of energy lost. To find the % of Gpe that wasnt transformed just divide (The difference of PE and KE/ Total GPE) x 100