Posted by Anonymous on .
A bungee jumper with mass 63.5 kg jumps from a high bridge. After reaching his lowest point, he oscillates up and down, hitting a low point eight more times in 40.0 s. He finally comes to rest 28.5 m below the level of the bridge. Calculate the spring stiffness constant AND the unstretched length of the bungee cord. Please help with step by step explanation!

physics help please!!! 
Anonymous,
Since he does 8 periods in 40 seconds 1 period takes 40s/8=5s, lets call this T. From formula T=2pii*sqrt(m/k) we can solve k (spring's stiffness constant). k=m/(T^2/(2pii)^2), k=100,275...N/m.
Then F=xk, where F is the stretching force caused by the jumper, F=mg, 63,5kg*9,81m/s^2=622,935N. x is the amount the thing has stretched so x=F/k, x=622,935N/100,275...N/m=6,2122m.
Thereby the cord's original lenght is 28,5m6,2122...m=22,2877...m.
Correctly rounded ansvers k=100N/m and unstretched lenght 22,3m.