A 4.00 mL syringe has an inner diameter of 5.00 mm , a needle inner diameter of 0.210 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.
Part A:What is the minimum force the nurse needs to apply to the syringe?
Part B: The nurse empties the syringe in 4.40 s . What is the flow speed of the medicine through the needle?
p = 140mmHg * 1.01e5Pa / 760mmHg = 18665 Pa
force against end of syringe
F = p*A = 18665Pa * π(0.00500m)²/4 = 0.366 N
Q = V / t = 4.00mL / 4.40s = 0.909 mL/s = 0.909 cm³/s
v = Q / A = 0.909cm³/s / (π(0.0210cm)²/4) = 2620 cm/s
or 26.2 m/s
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