Teacher Notes



Teacher Notes
Publication No. 13953
Pascal’s LawStudent Laboratory KitMaterials Included In Kit
String, thin, 75g ball
Syringe, plastic, 1mL, 8 Syringe, plastic, 3mL, 24 Syringe, plastic, 20mL, 16 Syringetip connectors, Luer Lock, 24 Additional Materials Required
Water, 200 mL
Beaker, 250mL Graduated cylinder, 50mL Mass, 1000g Meter stick Metric ruler Paper towels Spring scale, 1000g (10N) Tape Prelab Preparation
Safety PrecautionsWhen pressing on the syringe systems, be sure to press only the input plunger with your thumb and hold the output syringe with your other hand to prevent the syringes from separating. Do not use the syringe as a “squirt gun.” Wear safety glasses. Please follow all laboratory safety guidelines. DisposalEmpty the water in the syringes into a sink after completing the experiments. Consult your instructor for appropriate storage procedures. The materials should be saved for future use. Teacher Tips
Further ExtensionsAlternative Quantitative Investigation Setup {13953_Extensions_Figure_10}
To measure quantitatively, pull down on the spring scale to measure the force needed to lift the weights atop the large syringe. The frictional force can also be determined by measuring the force needed to raise the plunger with no mass on the plunger head. Reverse the equipment. Place weights atop the small plunger. How much force is needed to lift the weights atop the small syringe? Disassemble the equipment and pull out the plungers for both syringes. Measure the diameters of both plunger heads. Use the force and area determinations to calculate the pressure. The force from the weights is equal to mass times the acceleration due to gravity (mg), where g is equal to 9.81 m/s^{2}.
Correlation to Next Generation Science Standards (NGSS)^{†}Science & Engineering PracticesDeveloping and using modelsPlanning and carrying out investigations Using mathematics and computational thinking Analyzing and interpreting data Disciplinary Core IdeasMSPS2.A: Forces and MotionHSPS2.A: Forces and Motion Crosscutting ConceptsScale, proportion, and quantityEnergy and matter Systems and system models Performance ExpectationsMSPS22: Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object Sample DataData Table 1. {13953_Data_Table_1}
Data Table 2.
{13953_Data_Table_2}
Data Table 3.
{13953_Data_Table_3}
Answers to Questions
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Student Pages


Student PagesPascal’s LawIntroductionPascal’s law applies to many aspects of our lives. An extremely important application of Pascal’s law occurs when a driver presses on a brake pedal to stop a car. Pascal’s law is also at work when a mechanic easily lifts a car using a hydraulic jack. In this activity, hydraulics will be studied to gain a better understanding of the principles of Pascal’s law. Concepts
BackgroundBlaise Pascal (1623–1662) is well known as a mathematician. Pascal also had a strong interest in physical events and spent much of his time trying to explain the phenomena he witnessed in his experiments. He performed many experiments involving pressure in fluids. One of the most important principles he discovered became known as Pascal’s law. {13953_Background_Figure_1}
Mechanical advantage is a ratio of the output force compared to the input force (Equation 1). {13953_Background_Equation_1}
where
F_{o} is the output force {13953_Background_Equation_2}
where
d_{i} is the input distance {13953_Background_Equation_3}
Figure 2 shows a force of 20 Newtons pushing a fluid through a 1cm^{2} opening. Therefore, according to Pascal’s law, every square centimeter of the entire system is under a force of 20 N. The piston in the larger container has a surface area of 100 cm^{2}, making the amount of force lifting up the piston in the larger container equal to 2000‑N (20 N/cm^{2} × 100 cm^{2}). The total force increases as the surface area increases.
{13953_Background_Figure_2}
Materials
Water, 200 mL
Beaker, 250mL Graduated cylinder, 50mL Mass, 1000g Meter stick Metric ruler Paper towels Scissors Spring scale, 1000g (10N) String, 300cm and 60cm piece* Syringe, plastic, 1mL* Syringes, plastic, 3mL, 3* Syringes, plastic, 20mL, 2* Syringetip connectors, LuerLock, 3* Tape Safety PrecautionsWhen pressing on the syringe systems, be sure to press only the input plunger with your thumb and hold the output syringe with your other hand to prevent the syringes from separating. Do not use the syringe as a “squirt gun.” Wear safety glasses. Please follow all laboratory safety guidelines. ProcedureObservations
Student Worksheet PDF 