# physics

posted by Dr.B

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?

1. Damon

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

2. Dr.B

Thank you so much.

3. Damon

You are welcome.

4. Dr.B

excuse me, why did you add atm pressure to 15.3? your answer is true 100 present, but I did not understand this point.

5. Damon

Yes I did because the meters used measure relative, not absolute, pressure. (Relative is above one atmosphere)

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