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
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Energy at the height = mgh
This energy is converted to heat energy - mc\Deltat
∴ From the principle of energy conversion,
mc\Deltat = mgh
m x 450 x \Deltat = m x 10 x 20
∴ \Deltat = \(\frac{m \times 10 \times 20}{(m \times 450)}\)
= \(\frac{200}{450}\)
= \(\frac{4}{9}\)^\circC
Source: Myschool Past Questions Archive (Record #548)