A piece of substance of specific head capacity 450JKg-1K-1 falls through a vertical distance of 20m from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat. [g = 10ms-2]
-
A.
2/9°C -
B.
4/9°C -
C.
9/4°C -
D.
9/2°C
Correct Answer: Option B
Explanation
Energy at the height = mgh
This energy is converted to heat energy – mcΔt
∴ From the principle of energy conversion,
mcΔt = mgh
m x 450 x Δt = m x 10 x 20
∴ Δt = m x 10 x 20/(m x 450)
= 200/450
= 4/9°C