Question

A waterfall is 1.5 km high. If the temperature of water at its top is 20°C find its temperature at the bottom of waterfall, assuming all the kinetic energy is converted into heat energy.

[Take g = 10 ms⁻² and sp. heat capacity of water 4200 Jkg⁻¹°C⁻¹].

Answer 1

h = 1.5 km = 1500 m

Using the same energy conversion,

mgh = mcΔθ

$$\Delta\theta = \frac{gh}{c}$$

$$= \frac{10 \times 1500}{4200}$$

= 3.57°C

Final temperature = 20°C + 3.57°C = 23.57°C

In kelvin, T = 23.57 + 273.15 = 296.72 K