A child and sled with a combined mass of 53.0 kg slide down a frictionless hill that is 7.63 m high. If the sled starts from rest, what is its speed at the bottom of the hill?

Answer 1

PE -> KE

mgh = 1/2 mv^2
gh = 1/2 v^2
v = √2gh = √(2*9.8*7.63) = 12.23 m/s

note that the mass doesn't matter. Only the height contributes to the speed.