Pascal’s Principle With Syringes
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★★☆ Can be done by science teachers
Safety: ★★☆ Some safety precautions required to perform safely
Categories: Force, Pressure and Fluids, Simple Machines
Alternative titles: Hydraulic Force Demonstration
Summary
Using syringes connected with tubing, students can demonstrate Pascal’s Principle: when pressure is applied to a confined fluid, the pressure increase is transmitted equally throughout the fluid. This allows a small force applied on a small piston to generate a larger force on a larger piston.
Procedure
- Connect two syringes of different sizes with plastic tubing filled with water, ensuring no air bubbles remain.
- Push on the small syringe plunger and observe how the large syringe plunger is pushed outward with greater force but smaller movement.
- Push on the large syringe plunger and observe how the small syringe moves farther but with less force.
- Compare measured displacements of the plungers with calculated values based on piston areas and displaced volume.
- Discuss the tradeoff between force and distance, similar to a lever or other simple machines.
Links
Pascals Law syringe demo - Gyaneshwaran G:
📄 Proving Pascal’s Principle With Syringe Hydraulics - Scienceguyorg Ramblings: https://scienceguyorg.blogspot.com/2014/03/proving-pascals-principle-with-syringe.html
Variations
- Try different size ratios of syringes to see how the mechanical advantage changes.
- Measure the force required to move each syringe using a spring scale.
- Build a simple hydraulic arm using multiple syringes to show practical applications.
- Fill syringes with colored water to better visualize fluid movement.
Safety Precautions
- Ensure syringes and tubing are securely connected to prevent leaks.
- Avoid excessive force that could cause syringes to break or tubing to pop off.
- Use only water or safe liquids; do not use oils or chemicals.
- Supervise younger students to ensure safe handling.
Questions to Consider
- Why does a small piston create a larger force on a bigger piston? (Because the applied pressure is distributed over the larger piston area.)
- What is the tradeoff when using hydraulics? (Force is multiplied, but the distance of movement is reduced.)
- How is Pascal’s Principle applied in real life? (Hydraulic lifts, brakes, and machinery.)
- What happens if there is air in the system? (Air compresses, reducing efficiency and accuracy of force transmission.)