A 5.0 mL syringe has an inner diameter of 5.0 mm, a needle inner diameter of 0.2

Question

A 5.0 mL syringe has an inner diameter of 5.0 mm, a needle inner diameter of 0.21 mm, 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. What is the minimum force the nurse needs to apply to the syringe? Express your answer using two significant figures. The nurse empties the syringe in 3.2 s. What is the flow speed of the medicine through the needle? Express your answer using two significant figures.

Explanation / Answer

100 mm Hg = 13332.2 Pa

part a )

F = P*A

A = pi*d^2/4 = d = 5mm = 5 x 10^-3 m

F = 0.26 N

part b )

Q = v*A

Q = 5mL/3.2s = 5 * 10^-6 m^3/3.2 = 1.5625 x 10^-6 m^3/s

A = pi*d^2/4 = d = 0.21 mm = 0.21 x 10^-3

v = Q/A = 45.11 m/s = 45 m/s

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