A freestyle skier hits the take off ramp with an initial velocity of 17.5 m/s with a purely vertical take off (90 degrees). What is the peak height that the skier will reach?

Can you fully explain to me how to get this answer?
I did the formula d=Vi*deltT+(1/2)(a)(t^2). To get time did 17.5m/s/9.81m/s=1.78s. Got the answer 46.69 but the answer is 15.56. I got 15.56 on one side of my equation so idk what I'm doing wrong.

1 answer

You are using formulas without thinking.

at the peak height, the velocity is zero.

Vf=vi+at
0=17.5 + 9.8t
t= 1.78sec

hfinal=vi*time+1/2 g t^2
= 17.5*1.78-4.9(1.78^2)=15.6m