Question

The height of water fall is 210 m assuming that the surface on which the water is falling is perfectly insulated and all the kinetic energy of water is dissipated as heat. Find the rise in temperature of the water :

($g=10m/s^2$, Specific heat of water $=1000cal.K{g}^{-1}{C}^{-1}$ , 1 kcal$=$ 4200 J)

• A. ${0.1}^{0}C$
• B. ${0.5}^{0}C$
• C. $1^{0}C$
• D. ${0.25}^{0}C$

Answer 1

Answer: (B)

${0.5}^{0}C$

The entire potential energy of the waterfall will be converted into heat energy.

$mgH=mC\delta T$

$10\times 210=4200\times \delta T$

Thus, the rise in temperature will be close to ${0.5}^{o}C$.