physics
posted by Anonymous .
A child and sled with a combined mass of 40.0 kg slide down a frictionless hill. If the sled starts from rest and has a speed of 9.0 m/s at the bottom, what is the height of the hill?
m

Use energy:
gravitational potential energy: GPE = mgh
kinetic energy: KE = (1/2)m*v^2
By conservation of energy, GPEi+KEi = GPEf + KEf. (Final energy = initial energy).
At the bottom of the hill, GPEf = 0 (h=0). At the top of the hill, KEi = 0(v=0). Find the final kinetic energy, and from it, the final velocity.