Question

The human heart discharges $80ml$ of blood at each beat against pressure of $0.1mm$ of $Hg$ What is the power of the heart assuming that the pulse frequency is $75$ beats per minute? (Density of mercury $=13.6\times 10^{3}kg/m^3)$

• A. $1.33$ watt
• B. $121$ watt
• C. $1330k$ watt
• D. None

Answer 1

Answer: (A)

Volume of blood discharge/ beat $=80ml$
$=80\times 10^{-6}{m}^{-3}$
Pressure $=P=0.1mm$ of $Hg$
$P=0.1\times 13.6\times 10^3\times 9.8(P=h\rho g)$
$\frac{\text{ work done }}{\text{ beat }}=PV$
Total work done in 75 beat $=75\times PV$
Power $=\frac{\text{ work }}{\text{ time }}$
$P=\frac{0.1\times 13.6\times 10^3\times 9.8\times 80\times 10^{-6}\times 75}{60}$
$P=\frac{79968\times 10^{-3}}{60}$
$P=1332.8\times 10^{-3}$
$P=1.33$ watt