Final answer:
The question is related to Physics, focusing on the mechanical concept of energy usage and the effect of friction on motion while a hiker ascends an inclined plane with a 4% slope.
Step-by-step explanation:
The question pertains to the field of Physics and involves concepts such as energy usage, inclined planes, and the effects of friction on motion. Dissecting the question, we're examining a 68 kg hiker walking at 5.0 km/h up a 4% slope. To answer this, one would need knowledge of mechanics, specifically the work-energy principle and the relationship between force, mass, distance, and acceleration in the context of an inclined plane.
Calculating the energy expenditure or the work done by the hiker would involve considering the forces acting along the slope, the distance traveled, and any potential frictional forces. It can also be extended to find out how the 4% incline, which indicates the gradient of the slope, affects the hiker's energy usage as compared to walking on flat ground.