A skier starts from a hill 1000m high

[unholymist]

A skier starts from a hill 1000m high...

Homework Statement

A skier starts from a hill 1000m high. She skies down the slope a distance of 800m and passes a tree. During this time she has covered a horizontal distance of 700m.

a) Calculate her velocity, in km/h, as she passes the tree.
b) Explain why this is such an unreasonable answer.

Homework Equations

Energy, Motion, Forces as far as I know.

The Attempt at a Solution

http://dl.dropbox.com/u/4481894/%234%20attempt%201058.jpg

That's what I've done so far. I basically assumed no friction and, using trigonometry, solved for her acceleration parallel to the slope. Then, using the equations of motion, I solved for her final velocity parallel to the slope. Whether that was done correctly I am not sure of. However, I am stuck trying to find mass. In part B it asks to explain why that velocity is so unreasonable. I'm thinking it's because it would imply that her mass is quite huge... but I can't prove it with a number, lol.

Anyone want to help? :(

 

[Doc Al]

That's what I've done so far. I basically assumed no friction and, using trigonometry, solved for her acceleration parallel to the slope. Then, using the equations of motion, I solved for her final velocity parallel to the slope. Whether that was done correctly I am not sure of.

Looks good to me.

However, I am stuck trying to find mass.

Why are you trying to find the mass? (You won't be able to, given the information you have.)

In part B it asks to explain why that velocity is so unreasonable. I'm thinking it's because it would imply that her mass is quite huge... but I can't prove it with a number, lol.

Part B is a bit vague. I assume they want you to explain why such a high speed is not reasonable. What additional factors that you have neglected would limit the speed of a skiier?