I have the answer but i do not know how to slove it?

Question

Marc attaches a falling 500-kg object with a rope through a pulley to a paddle wheel shaft. He
places the system in a well-insulated tank holding 25 kg of water. When the object falls, it
causes the paddle wheel to rotate and churn the water. If the object falls a vertical distance of
100 m at constant speed, what is the temperature change of the water? (1 kcal = 4 186 J, the
specific heat of water is 4 186 J/kg°C, and g = 9.8 m/s2).

Answer: 4.7 C°

Answer 1

This is a question that can be answered by using the Conservation of Energy Principle.

The mass (on the rope) loses Potential Energy: P.E = mgh

The water is agitated and heats up, so ultimately this is the conversion of Potential Energy into HeatEnergy. (Internal Energy)
Q = m.s.(change of temperature)
where s is the specific heat capacity of the water
Equate the potential Energy cange to the heat energy change and solve the equation for the change in Temperature.

Answer 2

Since the speed is constant, there is no net force accelerating the object. Therefore the drag on the object by the rope equals its weight. The object falls 100m so the work done in holding the object at constant speed is its weight times 100m. Calculate that work (Joules) and then plug into the equation Q = m*c*delta T.