A child on a sled (m = 47.0 kg) slides down a long hill starting from a rest position at point 10.0 m or higher in elevation than his finish point.

a) What is the total mechanical energy present

b) Assuming that there is no friction or no external pushes, determine the child's speed at the bottom of the hill

c) The child speed at the bottom of the hill is actually 5.0 m/s. Explain whether or not this defies the law of conservation of energy