When the heart pumps blood into the aorta, the pressure gradient -the difference

Question

When the heart pumps blood into the aorta, thepressure gradient-the difference between the blood pressure inside the heart and the blood pressure in the artery-is an important diagnostic measurement. A direct measurement of the pressure gradient is difficult, but an indirect determination can be made by measuring the Doppler shift of reflected ultrasound. Blood is essentially at rest in the heart; when it leaves and enters the aorta, it speeds up significantly and-according to Bernoulli's equation-the pressure must decrease. A doctor using ultrasound of 2.5 MHz measures a 6500Hzfrequency shift as the ultrasound reflects from blood ejected from the heart.

What is the speed of the blood in the aorta? Assume that the speed of sound in human body is 1540 m/s

Explanation / Answer

speed of the blood in the aorta = velocity of sounding body x(6500/2.5 x 106)

=1540 x (6500/2.5 x 106) =4.004m/s

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