The SYSTOLIC pressure in a major artery is measured at 115 mmHg. What is the net force on a 1 cm2 section of the artery wall if the absolute pressure in the tissue outside the arterial wall is 108.6 kPa?
115 mm = 15.332 kPa
see
https://www.convertunits.com/from/mmHg/to/pascal
1 atm is about 101.3 kPa
and we are about
101.3 + 15.3 = 116.6 kPa absolute
so difference in presuure across wall
= 116.6 - 108.6 = 8 kPa = 8000 Pascals or Newtons / m^2
1 cm^2 = 10^-4 m^4
so our force is
8000 * 10^-4 = 0.8 Newtons
excuse me, why did you add atm pressure to 15.3? your answer is true 100 present, but I did not understand this point.
Thank you so much.
You are welcome.
Yes I did because the meters used measure relative, not absolute, pressure. (Relative is above one atmosphere)
Well, you've got a thorny question there! Let's dive right into it, funny bone first!
To calculate the net force acting on the artery wall, we need to find the pressure difference between the inside of the artery and the outside tissue.
First, let's convert that arterial pressure to the same units as the tissue pressure. 115 mmHg is roughly equivalent to 15.33 kPa.
Now, we can calculate the pressure difference:
15.33 kPa - 108.6 kPa = -93.27 kPa
Negative pressure? That's a bit deflating, isn't it? Negative pressure means that the force is actually being applied outward, away from the artery wall. So, the net force acting on that 1 cm² section of the artery wall is -93.27 kPa.
Hope that wasn't too much of a pressure for you! If you have any more questions, feel free to inflate my ego by asking!
To determine the net force on a section of the artery wall, we can subtract the external pressure from the internal pressure.
First, we need to convert the given values into matching units.
The systolic pressure is given in millimeters of mercury (mmHg), while the external pressure is given in kilopascals (kPa). We will convert both of them to pascals (Pa) because the SI unit for pressure is Pascal.
1 mmHg is equal to 133.322 Pa.
115 mmHg * 133.322 Pa/mmHg = 15,334.03 Pa (approx.)
1 kPa is equal to 1000 Pa.
108.6 kPa * 1000 Pa/kPa = 108,600 Pa.
Now that we have converted the values to pascals, we can calculate the net force on the artery wall.
Net Force = Internal Pressure - External Pressure
Net Force = 15,334.03 Pa - 108,600 Pa
Net Force = -93,265.97 Pa
The negative sign indicates that the force is directed inward, compressing the artery wall.
Therefore, the net force on the 1 cm^2 section of the artery wall is approximately -93,265.97 Pa.