First slide
Power
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 be 13.6 ×10-3 kg/m3 and g = 10 m/s2 then the power of heart in watt is

Moderate
Solution

Here,

Volume of blood pumped by man's heart,

V=5 litres =5×10-3 m3  1 litre =10-3 m3

 Time in which this volume of blood pumps, 

t=1min=60 s

 Pressure at which the blood pumps, 

P=150 mm of Hg=0.15 m of Hg

=(0.15 m)13.6×103 kg/m310 m/s2

(P=hρg)

=20.4×103 N/m2

   Power of the heart =PVt

=20.4×103 N/m25×10-3 m360 s=1.70 W

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