The heart of a man pumps 5 litres of blood through the arteries per minute at a pressure of 150 \mathrm{~mm} of mercury. If the density of mercury be 13.6 \times 10^{3} \mathrm{~kg} / \mathrm{m}^{3} and \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^{2} then the power of heart in watt is: (1) 1.50 (2) 1.70 (3) \quad 2.35 (4) 3.0
The heart of a man pumps 5 litres of blood through the arteries per minute at a pressure of 150 \mathrm{~mm} of mercury. If the density of mercury be 13.6 \times 10^{3} \mathrm{~kg} / \mathrm{m}^{3} and \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^{2} then the power of heart in watt is: (1) 1.50 (2) 1.70 (3) \quad 2.35 (4) 3.0

Solution: (2)
\begin{aligned} \text { Power } &=\vec{F}, \vec{V}=P A \vec{V}=\rho g h A V \\ &=13.6 \times 10^{3} \times 10 \times 150 \times 10^{-3} \times 0.5 \times 10^{-3} /_{60} \text { watt } \\ =& \frac{102}{60} \text { watt }=1.70 \text { watt. } \end{aligned}