A force platform is a tool used to analyze the performance of athletes measuring

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 62.0 kg athlete jumps down onto the platform from a height of 0.680 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.<br><br> F = (9 200 N/s)t - (11 500 N/s2)t2 <br>(a) What was the athlete's velocity when she reached the platform? <br>(b) What impulse did the athlete receive from the platform? <br>(c) WHAT IMPULSE DID THE ATHLETE RECEIVE FROM GRAVITY WHILE IN CONTACT WITH THE PLATFORM? <br>(d) With what velocity did she leave the platform? <br>(e) To what height did she jump while leaving the platform? <br>So, I have been able to do (a) v = -3.65m/s and (b) 982 N s.... but I need help with C, D, & E. Please help. PLEASE DO NOT COPY AND PASTE PREVIOUS QUESTIONS. I HAVE SEEN THEM AND SOME OF THEIR PARTS ARE WRONG!!

Explanation / Answer

C) The force of gravity is constant: F= mg = (62)(-9.8) = -607.6 N Ft = -607.6*(0.8) = -486.1 D) The net impulse must be equal to the change in momentum. Net impulse: 982 - 486.1 = 495.9 Initial momentum: -3.65*62 = -226.3 Final Momentum: 62*v Solve: 495.9 = 62*v - (-226.3) v= (495.9 - 226.3) / 62 = 4.35 m/s E) Vf^2 = Vi^2 + 2ad 0 = (4.35)^2 + 2(-9.8)*d d = (4.35)^2 /(2*9.8) = 0.97 m

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