The power expended is 500 W
Explanation:
First of all, we start by calculating the work done by the man in order to ascend: this is equal to the gravitational potential energy gained by the man, which is

where
m = 50 kg is the mass of the man
is the acceleration of gravity
is the change in height
Substituting,

Now we can calculate the power expended, which is given by

where
W = 2500 J is the work done
t = 5 s is the time elapsed
Substituting, we find

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Can't really plot a graph here for question 1.
2a) The car speeds up from A to B. The car travels at a constant speed from B to C. The car slows down to a stop from C to D.
b) From the graph, at 10 seconds, the car is moving at 20 m/s.
True. The question describes the idea of energy conservation faithfully. Energy can change forms but remains the same within an isolated system over time. Within such a system, energy cannot be created or destroyed.
Mass - Yes - Yes
Drop height - Yes - Yes
Initial velocity - No - No
Acceleration due to gravity - Yes - Yes
Object size - No - No
Hope this helps!
I think it is there is no change in the energy's sunlight