Question

The power of a heart which beats 72 times in a minute is $1.8\,W$. Calculate the work done by the heart for each beat.

Answer 1

Hint:
The power of the heart is defined as the ratio of the word done in a given amount of time to the time. Use this relation to calculate the work done by the heart in every minute.
Formula used:
$\Rightarrow {\text{Power = }}\dfrac{{{\text{work done}}}}{{{\text{time}}}}$

Complete step by step solution:
We’ve been given that a heart that beats 72 times in a minute uses power of $1.8\,W$. To calculate the work done by the heart, we can use the relation
$\Rightarrow {\text{Power = }}\dfrac{{{\text{work done}}}}{{{\text{time}}}}$
Since the power used by the heart has been given for one minute, and we want to find the work done by the heart in one minute, we can directly use the above relation and calculate work done for 1 min=60 sec as:
$\Rightarrow {\text{work done = power \times time}}$
$\Rightarrow {\text{ = 1}}{\text{.8}} \times {\text{60 = 108}}\,{\text{W}} $
So the work done by the heart in one minute when it beats 72 times is 108 W. Since 72 beats require 108 W, the work done for each beat can be calculated as
$\Rightarrow {\text{work done for 1 beat}} = \dfrac{{108}}{{72}} $
$\Rightarrow 1.5\,W $
So the work done by the heart for each beat is $1.5\,W$.

Additional Information
Medical devices like the pacemaker provide power to the heart to manually cause it to beat by converting electrical energy to mechanical energy to help control abnormal heart beats. The work done by the heart in each heart beat depends on various factors such as the amount of blood pumped, the size of the heart, etc.

Note:
Here we have assumed that the heart beats uniformly in a minute however in reality the heart beat fluctuates with time depending on the physical activity being carried out. As a result, the heart can have different work done for each heartbeat.