IIT JEE , AIEEE Forum - Physics , Mechanics

rakesh61

Heart discharges 75 cc of blood through the arteries ar each beat against an average pressaure of 10 cm of mercury Assuming pulse frequency of 72 / min the rate of working of heart in watt is

mercury density 13.6

g = 9.8

Ans 1.19 W

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iitkgp_bipin

Work done in one pump = PV = (

gh)V

= 13.6 g/cc = 13600 kg/m³ (convert the units properly)
g = 9.8 m/s²
h = 10 cm = 0.1 m
V = 75 cc = 75x10^-6 m³

Work done = (13600)(9.8)(0.1)(75x10^-6) = 0.9996 J

Heart pumps 72 times in 1min.
In 1 second it pumps 72/60 = 1.2 times

In 1 second work involved = (Work done in 1 pump)(No. of pumps in 1 second)

Power = (0.9996)(1.2) = 1.1995 W

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