1. During a rockslide, a 520 kg rock slides from rest down a hillside that is 500m long and 300m high. The coefficient of kinetic friction between the rock and the hill surface is 0.25
(a) If the gravitational potential energy U of the rock-Earth system is zero at the bottom of the hill, what is the value of U just before the slide?
(b) How much energy is transferred to thermal energy during the slide?
(c) What is the kinetic energy of the rock as it reaches the bottom of the hill?
(d) What is its speed then?
2. A worker pushed a 27kg block 9.2m block along a level floor at constant speed with a force directed 32degrees below the horizontal. If the coefficient of kinetic friction between block and floor was 0.20, what were (a) the work done by the worker's force
(b) the increase in thermal energy of the block-floor system?
The solution gives clear answers to the two classical physics questions posed with the aid of explanatory diagrams.