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

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