# Homework Help: Kinetic energy and gravitational potential energy questions

1. Nov 15, 2009

### Ilyo

1. An acrobat on skis starts from rest 50.0 m above the ground on a frictionless track and flies off the track at a 45.0 degree angle above the horizontal and at a height of 10.0m. disregard air resistance. what is the skier's speed when leaving the track?

2. K=.5M*V^2 and U=M*g*h

3. I don't have a attempt at the solution not because I am trying to get you to do my homework but because I don't understand the question I am having trouble picturing the scene what does it mean by the horizontal and the 45 degree angle. What is needed and what is just fluff... Can someone help?

2. Nov 15, 2009

### srmeier

Before the skier starts down the hill his potential energy is maximum. The skier converts his potential energy to kinetic as he travels down the incline. So I ask you this: when is the skiers kinetic energy at a maximum and what is the skiers potential the moment he leaves the ramp?

It will help you to associate velocity with kinetic energy. When is the velocity the highest, When is it the lowest?

also note: potential energy is a function of position, kinetic energy is a function of velocity

3. Nov 15, 2009

### Ilyo

what I don't get is how do we get the skiers mass with the given info

4. Nov 15, 2009

### srmeier

When we write our equation we get this:

$$.5mv^2=m(9.8)(40)$$ (e.i potential energy is converted to kinetic)

If you notice, $$m$$ reduces to 1. That is why we don't need the mass ^^