A body of mass 20 kg fell from a height of 42.3 m above the surface of the ground. Find the sum of its kinetic energy and its potential energy relative to the ground 2 seconds after it started falling. Take .
A body of mass 7 kg fell vertically from point to the ground. Given that, when it reached the ground, its kinetic energy was 3 724 joules, find its gravitational potential energy relative to the ground when it was at point . Consider the acceleration due to gravity to be 9.8 m/s2.