Answer:
180 W
Explanation:
The work done by the man against gravity is equal to its gain in gravitational potential energy:

where
(mg) = 720 N is the weight of the man
is the change in height
Substituting,

The power he must deliver is given by

where
W = 3600 J
t = 20 s is the time taken
Substituting,

Answer:
Explanation:
The hand provides Kinetic Energy in moving.
The KE is transformed to Frictional energy
The Frictional Energy can produce heat and light energy.
The sandpaper produces little shreds from the grit of the paper.
The shreds have KE (they move)
Answer: when fish is stunning it's prey it's cause electric shock to the prey that's make it die and be able to be utilized by electric eel(fish generate electric surround)