physics
posted by Vishnu on .
A skier is gliding along at 1.13 m/s on horizontal, frictionless snow. He suddenly starts down a 13.1° incline. His speed at the bottom is 18.8 m/s. What is the length of the incline?

Use his change in kinetic energy to get his loss of potential energy. The equation
g H = change in (V^2)/2
can be used to het the height change, H.
H and the slope angle can be used to get the length L of the incline.
H/L = sin 13.1

My attempt:
H/L = sin 13.1
L = sin13.1 / H
= sin13.1 / 18.8 m/s
= 0.01 km = 10 m
Why is this answer incorrect?
Responses
physics  drwls, Wednesday, October 8, 2008 at 2:10am
Your equation L = sin13.1 / 18.8 m/s
is totally wrong. You cannot have a length on one side of an equation and 1/Velocity on the other side. It is not even dimensionally correct. You did not follow the method suggested. Where did the L = 0.01 km come from?
The change in V^2/2 is (18.8^2  1.13^2)/2 = 176.1 m^2/s^2
That equals the change in gH
The change in H is therefore
176.1 m^2/s^2 / 9.8 m/s^2 = 18.0 m
physics  Luckna, Wednesday, October 8, 2008 at 9:35am
This answer still shows up as incorrect

I computed H for you. They asked for the length L of the incline. Did you do the final step to get L?
We usually don't do complete answers for students. We try to teach you the method to solve problems yourself. 
I agree with DrWLS.

Can i have the formula for this step please?

You know h is the height, you know the angle, and you are looking for the hypotenuse. Could the formula be the sine function?

h =18.0 m
angle = 13.1°
hypotenuse = ?
Sine function formula is:
Opposite / hypotneuse
What is opposite?