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Solution


Q.

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 13.6×103kg/m3 and g=10m/s2, then the power (in watt) is           [2015]
1

3.0

 

2

1.50

 

3

1.70

 

4

2.35

 


Ans.

(3)

Here, Volume of blood pumped by man's heart,

V=5 litres=5×10-3 m3  (∵1litre=10-3 m3)

Time in which this volume of blood pumps,

            t=1min=60s

Pressure at which the blood pumps,

P=150mm of Hg=0.15m of Hg

=(0.15m)(13.6×103kg/m3)(10m/s2)

=20.4×103N/m2

∴ Power of the heart =PVt

        =(20.4×103N/m2)(5×10-3m3)60s=1.70W