Question

Water is falling from 160m height. Assuming that half the K.E. of falling water gets converted into heat, the rise in temperature of water is approximately

• A. ${0.1}^{0}C$
• B. ${0.2}^{0}C$
• C. ${0.3}^{0}C$
• D. ${0.4}^{0}C$

Answer 1

The correct option is B ${0.2}^{0}C$

As the water falls from 160m height, its potential energy is converted into kinetic energy.
Given that half of the KE is converted to heat energy, essentially means half of PE is converted.
$\frac{1}{2}mgh=mc\Delta T$
$\Rightarrow \Delta T=\frac{0.5\left(gh\right)}{c}=\frac{0.5\left(10\right)\left(160\right)}{4200}={0.19}^{o}C$