The correct option is B 26.65∘C
Given,
Mass of iron block, m1=1kg
Mass of water, m2=1kg
Initial temperature of iron block, T1,0=300∘C
Initial temperature of water, T2,0=30∘C
Specific heat of iron, c1=460 J kg−1 K−1
Specific heat of water, c2=4200 J kg−1 K−1
Let the final temperature of the mixture be T.
Heat gained by water equals the heat lost by iron sphere.
m1c1(T−T1,0)=m2c2(T2,0−T)
T=m1c1T1,0+m2c2T2,0m1c1+m2c2
T=1×460×300+1×4200×301×460+1×4200 ∘C
T=56.65∘C
Increase in the temperature of water is:
ΔT2=T−T2,0
ΔT2=(56.65−30) ∘C=26.65∘C