Find H of a Ski Jump: Solving a Projectile Motion Problem

[chaotixmonjuish]

A skier (m=59.00 kg) starts sliding down from the top of a ski jump with negligible friction and takes off horizontally. If h = 7.70 m and D = 12.90 m, find H.

img:http://i242.photobucket.com/albums/ff106/jtdla/prob21a.gif

I was given a hint to treat the skier as a projectile, so I broke the skier's position into two parts.

yf=yi+vt+1/2gt^2
0=7.70+Vt+4.7t^2

xf=x0+Vt
12.9=0+vt
then solve for t in the x
12.90/vt

so I sub that back into y

0=7.70+v(12.90/v)-4.7(12.90/v)^2

I get a velocity of 8.89 m/s

am I doing this right

 

[chaotixmonjuish]

6.2915 m/s, I just realized that I used 4.7 instead 4.9

I also got H=13.38m

Am I about right?

 

[chaotixmonjuish]

any response please?

 

[learningphysics]

In the vertical direction when the person is going off the ramp horizontally:

dy = v1y*t + (1/2)at^2, but v1y = 0

dy = (1/2)at^2

dy = -4.9t^2

plug in dy = -7.7

-7.7 = -4.9t^2

solve for time. then get the horizontal velocity using D = v*t

Then use energy...

mgH = mgh + (1/2)mv^2