1. The problem statement, all variables and given/known data An 80 kg skydiver jumps from an altitude of 1000m and opens his chute at 200m (a) The total retarding force on the diver is a constant 50.0N without his chute open, it is constant 3600N with his chute open. What will be the skydiver's speed when he reaches the ground? 2. Relevant equations (sum)F=ma P.E.=mgy K.E.=(1/2)mv^2 E(total)=P.E. + K.E. 3. The attempt at a solution Well, frankly I've gone through several methods and it's all become a big mess. It seems like a straight forward problem but I think I've gotten tunnel vision from it and am missing something obvious. I have a hunch I should be using PE and KE rather than the following methods, but this was all I could come up with. I got a velocity (at 200m)=122 m/s doing this: (sum)F=ma 750N=80a a=9.375 m/s/s --> 200=1000+V(initial)t+.5at^2 =200=1000+.5*9.375*t^2 t=13s (appox.) V(@200)=9.375*13=122 m/s (sum)F=ma -3500N=80a a=-35 m/s/s 0=200+122t=.5*(-35)*t^2 t= 8.34 (or -1.3... obviously time can't be negative) V(final)=V(@200)-35*8.34 V(final)=-170 m/s.... this does not seem right at all to me. Any suggestions? I had tried using PE and KE to solve for it, but got lost along the way.