A hypodermic needle of length 3 cm and internal diameter of 45 mm is used to draw blood with viscosity of 4 mPl. Assuming the pressure difference across the needle is 80 cmHg, how long does it take to draw 15 mL?
Fluid Pressure
The term fluid pressure is coined as, the measurement of the force per unit area of a given surface of a closed container. It is a branch of physics that helps to study the properties of fluid under various conditions of force.
Gauge Pressure
Pressure is the physical force acting per unit area on a body; the applied force is perpendicular to the surface of the object per unit area. The air around us at sea level exerts a pressure (atmospheric pressure) of about 14.7 psi but this doesn’t seem to bother anyone as the bodily fluids are constantly pushing outwards with the same force but if one swims down into the ocean a few feet below the surface one can notice the difference, there is increased pressure on the eardrum, this is due to an increase in hydrostatic pressure.
- A hypodermic needle of length 3 cm and internal diameter of 45 mm is used to draw blood with viscosity of 4 mPl. Assuming the pressure difference across the needle is 80 cmHg, how long does it take to draw 15 mL?
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