Question

Two stones each of mass 5kg fall on a wheel from a height of 10m. The wheel stirs 2kg water. The rise in temperature of water would be

• A. ${2.6}^{\circ }C$
• B. ${1.2}^{\circ }C$
• C. ${0.32}^{\circ }C$
• D. ${0.12}^{\circ }C$

Answer 1

The correct option is D

${0.12}^{\circ }C$

For the given condition potential energy of the two masses will convert into heat and temperature of water will increase $W=JQ\Rightarrow 2m\times g\times h=J\left(m_{w}S\Delta t\right)\Rightarrow 2\times 5\times 10\times 10=4.2(2\times {10}^3\times \Delta t)$

$\therefore \Delta t=\frac{1000}{8.4\times {10}^3}={0.119}^{\circ }={0.12}^{\circ }C$