Answer
(a) decrease
(b) stay the same
(c) decrease
Work Step by Step
(a) We know that the gravitational potential energy is directly proportional to the height. While moving down the hill, the height is decreasing from the ground level and hence the gravitational potential energy will also decrease.
(b) We are given that a constant speed is maintained and since we know that the kinetic energy is dependant on the speed, the kinetic energy will stay the same because the speed does not change.
(c) We know that in the given scenario, the kinetic energy doesn't change but due to the decrease in gravitational potential energy, the mechanical energy will decrease.
