A force platform is a tool used to analyze the performance of athletes measuring the vertical force that the athlete exerts on the ground as a function of time. Starting from rest, a 66.0 kg athlete jumps down onto the platform from a height of 0.770 m. While she is in contact with the platform during the time interval 0

Question

A force platform is a tool used to analyze the performance of athletes measuring the vertical force that the athlete exerts on the ground as a function of time. Starting from rest, a 66.0 kg athlete jumps down onto the platform from a height of 0.770 m. While she is in contact with the platform during the time interval 0 < t < 0.8 s, the force she exerts on it is described by the function below.
F = (9 200 N/s)t - (11 500 N/s2)t2 
Assume the positive y-axis points upward.

(d) With what velocity did she leave the platform?

myname · Answer

I got the Impulse which is 981.3504 Ns

myname · Answer

And i have this equation----> Vf -Vi = 14.868

myname · Answer

How do i get the initial velocity