1) 24500 J (29400 J if we include also the water)
The gravitational potential energy of an object is given by:

where m is the mass, g is the gravitational acceleration and h is the heigth above the ground.
Therefore, the gravitational potential energy of the cylinder is given by:

If we count also the water inside the cylinder, the total mass is 5.0 kg + 1.0 kg = 6.0 kg, and the total gravitational potential energy would be

2) 24530 J
The heat energy added to the water is given by:

where
m = 1.0 kg is the mass of the water
C = 4186 J/kg C is the specific heat of the water
is the increase in temperature
Substituing, we find

3) 1.0 kg
The mass of the water is given, and it is m = 1.0 kg.
4)

The temperature change of the water is the difference between its final temperature and its initial temperature:

5)

The specific heat of the water is
