What is the velocity of medicine emerging from a hypodermic syringe?

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SUMMARY

The discussion focuses on calculating the velocity of medicine emerging from a hypodermic syringe using fluid dynamics principles. Given a cross-sectional area of 2.5x10e-5 m² and a force of 2N applied to the plunger, the initial pressure (P1) is calculated as 80,000 Pascals. The Bernoulli equation is applied, leading to the conclusion that the exit pressure (P2) can be assumed to be 0, as the only external pressure is atmospheric. This assumption is critical for determining the velocity of the fluid as it exits the syringe.

PREREQUISITES
  • Understanding of Bernoulli's equation
  • Basic principles of fluid dynamics
  • Knowledge of pressure calculations (P = F/A)
  • Familiarity with hypodermic syringe mechanics
NEXT STEPS
  • Study the application of Bernoulli's equation in various fluid systems
  • Explore the relationship between pressure and velocity in fluid dynamics
  • Learn about the effects of cross-sectional area on fluid flow rates
  • Investigate the mechanics of hypodermic syringes and their design considerations
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Students and professionals in physics, engineering, and medical fields who are interested in fluid dynamics and the mechanics of syringes will benefit from this discussion.

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1. A hypodermic syringe contains a medicine with a density of water. The barrel of the syringe has a cross-sectional area of 2.5x10e-5 m^2. A force of 2N is exerted on the pluger (left, larger side). Determine the velocity of the medicine as it emerges from the needle

_________
\
\
(1) (2)=====
/
_________/

2. P1 + 1/2pV1^2 + pghi = P2 + 1/2pV2^2 + pghf

Area = 2.5x10e-5 m^s, Force = 2 N

P1 = F/A = 80,000 Pascals

Because Area decreases, Velocity increases decreasing pressure so we assume P2 = 0, is this correct why we make P2 = 0?
 
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Inside the syringe pressure in the liquid is sum of atmospheric pressure and pressure due 2N force. Outside the syringe there is only atmospheric pressure.
 

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