Question

The human heart is a powerful and extremely reliable pump. Each day it takes in and discharges about 7500 L of blood. Assume that the work done by the heart is equal to the work required to lift this amount of blood a height equal to that of the average American woman (1.63 m). The density (mass per unit volume) of blood is 1.05×103kg/m3. (a) How much work does the heart do in a day? (b) What is the heart’s power output in watts?

Answer 1

Answer:

(a) 1.257 x 10^5 J

(b) 1.456 Watt

Explanation:

Volume of blood, v = 7500 L = 7.5 m^3

Height, h = 1.63 m

density of blood, d = 1.05 x 10^3 kg/m^3

(a) work done = m x g x h

W = v x d x g x h = 7.5 x 1.05 x 1000 x 9.8 x 1.63 = 1.257 x 10^5 J

(b) time = 1 day = 24 x 60 x 60 s = 86400 seconds

Power = Work / time = 1.257 x 10^5 / 86400 = 1.456 Watt