Such an oscillator-in-a-box system can be used to model the relationship between

Question

Such an oscillator-in-a-box system can be used to model the relationship between the apparent weight of a person and the motion of the blood in his body. Specifically, the block represents the centre of mass of the blood, the box represents the rest of the human body, and the force of the spring represents the force the heart exerts on the blood. The acceleration of the blood can be monitored by measuring the apparent weight of the person. A device based on this mechanism is known as a ballistocardiographic (BCG) scale 2. A ballistocardiographic scale is essentially a very sensitive scale to measure and record a patient's apparent weight. The patient stands upright on the scale. As his heart beats, his apparent weight changes as a result of the acceleration of the blood in the vertical direction. In a typical case, a patient's mass is 65kg. His heart pumps about 0.075kg of blood on each contraction into the aorta, reaching a maximum upward velocity of 1.0m/s in 0.13 seconds. Estimate the change in the patient's apparent weight.

Explanation / Answer

We can say

a=v/t=1/0.13=7.69 m/s^2

We know weight of person will act downward

Apparent weight channge=0.075*a=0.57 N

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