Question

The human heart discharges $75c{m}^3$ of blood per beat against an average pressure of $10cm$ of $Hg$. Assuming that the pulse frequency is $75/minute$, the power of the heart is (density of $Hg=13.6gm/c{m}^3$):

• A. $1.275W$
• B. $12.5W$
• C. $0.125W$
• D. $125W$

Answer 1

Answer: (A)

$1.275W$

Force $=pressure\times area$
$=10\times 136\times {10}^3\times Area\times {10}^{-2}\times 10$
Power $=F.v$
$=10\times 13.6\times {10}^3\times Area\times v\times {10}^{-1}$
$=10\times 136\times {10}^3\times \left(volume/sec\right)\times {10}^{-1}$
$=10\times 13.6\times {10}^3\times \frac{75\times 75}{60}\times {10}^{-6}\times {10}^{-1}$
$=1.275W$