Please help A 1.0 m L syringe has an inner diameter of 5.5 m m , a needle inner

Question

Please help

A 1.0mL syringe has an inner diameter of 5.5mm, a needle inner diameter of 0.22mm , and a plunger pad diameter (where you place your finger) of 1.2 cm. A nurse uses the syringe to inject medicine into a patient whose blood pressure is 140/100. Assume the liquid is an ideal fluid.

Part A:

What is the minimum force the nurse needs to apply to the syringe?

Express your answer using two significant figures.

Part B

The nurse empties the syringe in 3.8s . What is the flow speed of the medicine through the needle?

Express your answer using two significant figures.

Explanation / Answer

assumptions:
1) The internal P must overcome the highest Blood pressure
2) Only the fluid pressure requires force. (which is false). Neglect the friction force needed to move the plunger against the friction of the inner wall of the syringe.

A) is a pressure, force area problem

B) is a volume flow speed problem

C) the area of the push pad does not matter, it is the force in Newtons. by the finger which is required
.
A) change blood pressure in mm Hg to pressure in Newtons/ sq ml. P max
P blood ( high ) = P inside syringe = F finger/ A cross section of barrel, not A of Plunger pad or needle hole
B)
Vol / time in ml/sec
= flow speed through needle hole

In 1 sec a cylinder of fluid vol = length, (Vel x1 sec) passes through. x A, cross section of needle hole.
T= 4.3 sec, Vol = 1.0 ml find Vel in appropriate speed units,
Cm/ sec or mm/sec or M/sec

I don't want to struggle with the units either.

this is a mixed unit problem which is confusing
the information about the pad diameter is not important. Except to determine the pressure , not the force, of the finger on the push pad.
Notice the push pad diameter is not the same as the inside of the syringe

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