Question

A device used since the 1940s to measure the kick or recoil of the body due to heart beats is the "ballistocardiograph." What physics principle(s) are involved here to measure the force of cardiac contraction? How might we construct such a device?

a) Conservation of momentum.
b) Newton's third law.
c) Archimedes' principle.
d) Pascal's law.

Answer 1

The ballistocardiograph measures the reaction force of the body caused by the force of cardiac contraction using Newton's third law. A BCG can be constructed with either a sensor on the body or a moving table. While BCG was once widely used, ECG and ECHO are now more common in cardiology diagnostics.

Step-by-step explanation:

The device used to measure the kick or recoil of the body due to heart beats since the 1940s is known as the ballistocardiograph (BCG). The principle of physics involved in this measurement is Newton's third law, which states that for every action, there is an equal and opposite reaction.

When constructing a ballistocardiograph, one could use a sensor placed directly on the person or a moving table suspended from the ceiling. Upon the heart beating and forcing blood into the aorta, the body experiences a reaction force in the opposite direction, which is what the ballistocardiograph measures. Although the BCG provides information on the strength of the heart beat and the volume of blood ejected, other diagnostic tools like the electrocardiogram (ECG) and echocardiogram (ECHO) have become more prevalent in cardiology.