physics
posted by brooke .
An 85 kg football player traveling 4.7 m/s is stopped in 1.0 s by a tackler. What is the original kinetic energy of the player? (I tried using 1/2 m v^2 but that doesn't seem to be right. How do I manipulate the formula?) What average power is required to stop him?

It is right, 1/2 m v^2 is the original KE.
average power= energy/timestopping 
50 joules

934 joules