Answer:
C. 2 kg
Explanation:
From the problem , it appears that due to fall by 800m (h ) , potential energy is converted into heat energy which increases the temperature of water . Let the mass of cylinder falling be M , h be the height
loss of potential energy = Mgh
heat generated = Mgh
let heat generated increases a temperature rise of Δt in the mass of water m
heat absorbed = msΔt , s is specific heat of water .
msΔt = Mgh
Δt = Mgh / ms
Δt = K / m ( M , g , h and s are constant in both the case)
For first case ,
m = 2 kg and Δt = 2.4
2.4 = K / 2
K = 4.8
For second case
Δt = K / m
1.2 = 4.8 / m
m = 4 kg
mass added = 4 - 2
= 2 kg .