A piece of substance of specific head capacity 450JKg-1K-1 falls through a vertical distance of...

JAMB 1999

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

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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

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