Answer:
The average power the student expended to overcome gravity is 560W, Watts is a units of work it is Joules /time or kg*
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Explanation:
Weight = 700N

The power is the work in (Joules) or (N*m) in a determinate time (s) to get Watts (W) units for work

Answer:
Average speed in east direction
Explanation:
We have given average speed of the entire trip = 5 km/hr
First the car 4 hours then travels 12 km in 4 hours
So total time of the trip = 4+4 = 8 hours
So total distance traveled in the trip 
As the car travel 12 km in 4 hours to the west
So distance traveled in 4 hour in east = 40 -12 = 28 km
Time in east direction = 4 hour
So average speed in east direction 
The first law of thermodynamics can be written as

where

is the variation of internal energy of the system

is the amount of heat absorbed by the system

is the work done by the system on the surrounding.
Using this form, the sign convention for Q and W becomes:
Q > 0 --> heat absorbed by the system (because it increases the internal energy)
Q < 0 --> heat released by the system (because it decreases the internal energy)
W > 0 --> work done by the system (for instance, an expansion: when the system expands, it does work on the surrounding, and so the internal energy decreases, this is why there is a negative sign in the formula Q-W)
W < 0 --> work done by the surrounding on the system (for instance, a compression: when the system is compressed, the surrounding is doing work on the system, and so the internal energy of the system increases)