A heart exerts a maximum (systolic) pressure of 152mm Hg. This pressure is applied to an aorta of cross sectional area 2.0cm2 What force must be generated by the heart in order to apply this pressure? (Take 760mm Hg to be 1.0 atmosphere which is 100kPa.)

Answer:

25) B

760 mm Hg has a force of 100kPa.
152 m Hg would have a force of = [(152 ÷ 760) x 100] = [0.2 x 100 kPa] = 20 kPa = 20 x 10³ Pa

2.0 cm² = 0.0002 m²

Pressure = Force ÷ Area

20 x 10³ Pa = Force ÷ 0.0002

Force = 20 x 10³ Pa x 0.0002 = 4 N