Question

The heart of a man pumps 5 litres of blood through the arteries per minute at a pressure of 150 $mm$ of mercury. If the density of mercury is $13.6\times {10}^{3}kg/m^3$ and $g=10m/s^2$ , then the power of heart in Watts is

• A. $1.50$
• B. $1.70$
• C. $2.35$
• D. $3.0$

Answer 1

Answer: (B)

$1.70$

Given,
$\rho =13.6\times {10}^3\frac{kg}{m^3}$, $h=150\times {10}^{-3}m$,

Rate of blood flow = $Av=\frac{5\times {10}^{-3}}{60}$

We know that,
$Power=\overrightarrow{F}\cdot \overrightarrow{v}=PAv=\rho gh\times$ $Av$

[Since Pressure = $P=\frac{F}{A}$]
$Power=(13.6\times {10}^3)\times 10\times (150\times {10}^{-3})\times \left(\frac{5\times {10}^{-3}}{60}\right)$
$Power=1.7Watt$
Thus the power of heart is 1.7 Watts.