NECO 2001 Physics · Question 39

A waterfall is 630m high. What is the change in temperature of a quantity of water that falls from the top to…

Question

A waterfall is 630m high. What is the change in temperature of a quantity of water that falls from the top to the bottom of the waterfall? (Neglect heat losses to the surroundings, take g as 10 $ms^{-2}$ and specific heat capacity of weather as 4200J kg-1K-1

A.0.015°C
B.1.50°C
C.15.00°C
D.21.00 °C
E.50.00°C

Answer: B. 1.50°C

Explanation written with AI and checked against the answer key

Analyze the question: Water falls through 630 m. Its potential energy is converted to heat, which raises the water's temperature. We are asked for the temperature change. Concept: All the loss in gravitational potential energy becomes heat energy in the water. mgh = mcΔθ The mass cancels, so: Δθ = gh / c Solution: Δθ = (10 × 630) / 4200 Δθ = 6300 / 4200 Δθ = 1.5 °C Answer: The change in temperature is 1. Tip: When a question says "falls from a height" and asks for a temperature change, set mgh = mcΔθ. The mass cancels, so you never need it. Also, 6300/4200 simplifies quickly to 63/42 = 1.5, so check for easy simplifications before using a calculator.

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