A 1.63 mL syringe has an inner diameter of 6.34mm, a needle inner diameter 0.25
ID: 1752545 • Letter: A
Question
A 1.63 mL syringe has an inner diameter of 6.34mm, a needle inner diameter 0.25 mm, and a plunger pad diameter(where you place your finger) of 1.09 cm. A nurse uses the syringeto inject medicine into a patient whose blood pressure is 140/100.What is the minimum force the nurse needs to apply to thesyringe? The nurse empties the syringe in 2.24 s. What isthe flow speed of the medicine through the needle? A 1.63 mL syringe has an inner diameter of 6.34mm, a needle inner diameter 0.25 mm, and a plunger pad diameter(where you place your finger) of 1.09 cm. A nurse uses the syringeto inject medicine into a patient whose blood pressure is 140/100.What is the minimum force the nurse needs to apply to thesyringe? The nurse empties the syringe in 2.24 s. What isthe flow speed of the medicine through the needle?Explanation / Answer
Cool problem. Anyway, the blood pressure is measured in millimetersof Hg. Let's convert that into pascals(pressure). We convert the140 part of 140/100. Conversion: 140mm*(1 atm)/760mm*(101.3 kPa)/1atm*(1000 Pa)/(1 kPa) =18660 Pa Now we know that 140 mm Hg=18660 Pa. Before we find the force, wehave to find the area of the needle. Area of needle=(0.000125)2 =0.000000049m2 We have it in m2 because Newtons uses m not mm. Let's find the force now. P=F/A 18660=F/0.000000049m2 =0.0009 N That was for the first part of your question. Now, let's find the flow speed. If the nurse empties 1.63 mL in2.24 seconds, then the flow speed is .72 mL/s. That is the flowrate and it is constant. It will be the same everywhere in thesyringe. But we're not done yet. We need to find the velocity of the medicine through the needle. Sothen, Area x Velocity = Constant. Av=.72 mL/s If we do V= .72/0.000000049, then we will get our answer inm/s.Let's change it to V=.72/.049. so our answer will be in mm/s (there will be less zerosthis way). =14.69 mm/s So for the first part, it is 0.0009 N, and for the second part, itis 14.69 mm/s.
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