A 21-kg child starts from rest and slides down a slide that is 1.8 m high. At the bottom of the slide, the child is moving 0.56 m/s.

Question

How much work, in joules, was done by the nonconservative force of friction on the child? 

Answer 1

At the top of the slide, the child has gravitational potential energy only = mgh = 370.44 Joules

At the bottom, the child has zero potential energy and a kinetic energy of (0.5)mv^2 = 3.29 Joules.

Therefore the work done by non conservative forces = 367.15 J