If the sled starts from rest, what is its speed at the bottom of the hill

Question

i need help in finding the answer

here is the question 

A child and sled with a combined mass of 50.2 kg slide down a frictionless hill that is 8.20 m high. If the sled starts from rest, what is its speed at the bottom of the hill

Answer 1

Find the potential energy at the top of the hill, where the kinetic energy is zero, and the potential energy is the total energy.   Set it equal to the kinetic energy at the bottom of the hill, where the potential energy is zero, and the kinetic energy is the total energy.  Solve for the speed.

 

m = mass of sled + mass of child = 50.2 kg

h = height of hill = 8.20 m

 

mgh = mv²/2

 

gh = v²/2

 

v = √(2gh) = √[2(9.8)(8.2)] m/s ≅ 12.68 m/s