How Does Projectile Motion Apply in Olympic Ski Jumping?

[nerdmon]

Homework Statement

In the 2006 Winter Olympics, Thomas Morgenstern of Austria won a gold medal in one of the ski jumping events; his longest jump was R=140.0 m.

He takes off from point A at the top of a mountain at an angle of 15.0 degrees above the horizontal, with an initial speed of v0 = 26.9 m/s. His trajectory is that of a parabolic pathway, in which he lands at point B. The landing hill is curved and is quite steep near point B. You should ignore air resistance in this problem.

a) How long is he in the air? (From point A to B)
b) Find the magnitude and the direction of his velocity just before he lands at B
c) Based on your answer to part (b), explain why it is safer for ski jumpers to land on a steep slope than on a flat surface. (Hint: a large sudden change in velocity requires a large impact force.)

Homework Equations

deltax=v0t + 1/2at^2
uhh i don't know what else to use

The Attempt at a Solution

for a i did:
140=26.9t
t = 5.20 sec (is this right?)
and then i didn't know how to do b

 

[andrevdh]

For a) you need to use the horizontal speed, not the initial speed, which is directed fifteen degrees above the horizontal.