Justin, with a mass of 30 g, is going down a 8.0 m high water slide. he starts at rest, and his speed at the bottom is 11 m/s. how much thermal energy is created by friction during his descent

The thermal energy is the work done by friction. If Justin is at rest intially, his potential energy is MGH. Hence we have 30* 9.8*8 = 2352N. Where m is mass, g accleration due to gravity, and h is the height. When he gets to the bottom of the slide, his potential energy is converted to usable kinetic energy, so we have 1/2 mv^2. We end up with 1/2 * 30 * (11)^2 = 1815N. He started with 2352N and ended up with 1815N. Hence the thermal energy is 2352 - 1815 = 537N.

Your answer would be false