Question

The height of a waterfall is 84 metre. Assuming that the entire kinetic energy of falling water is converted into heat, the rise in temperature of the water will be

$(g = 9.8m/s^{2},\mspace{6mu} J = 4.2joule/cal)$

• A. 0.196°C
• B. 1.960°C
• C. 0.96°C
• D. 0.0196°C

Answer 1

Answer: (A)

0.196°C

Answer 2

$W = JQ$ ⇒ $mgh = J(m.c.\Delta\theta)$

⇒ $\Delta\theta = \frac{gh}{Jc} = 0.0023h = 0.0023 \times 84 = 0.196{^\circ}C$