A syringe with a plunger of diameter 1.6 cm is attached to a hypodermic needle with a diameter of 2.5 mm.What minimum force must be applied to the plunger to inject into a vein in which the pressure is 2265.9 Pa?
A)0.05 N
B)0.15 N
C)0.30 N
D)0.46 N
E)0.60 N

Question

Quizplus · Accepted Answer

We can use the formula for pressure:
Pressure = Force/Area

The area of the plunger is:
Area = πr^2
Area = π(0.8 cm)^2
Area = 2.01 cm^2

Converting to meters:
Area = 2.01 × 10^-4 m^2

The area of the hypodermic needle is:
Area = πr^2
Area = π(1.25 × 10^-3 m)^2
Area = 4.91 × 10^-6 m^2

The total force required is:
Force = Pressure × Area
Force = 2265.9 Pa × (2.01 × 10^-4 m^2 - 4.91 × 10^-6 m^2)
Force = 0.46 N

Therefore, the minimum force required is 0.46 N, which is choice D.

A Syringe with a Plunger of Diameter 1