Chapter 3 Section 2 Notes

Fluid  Any substance that has the ability to flow (move on its own) Two States ○ ____________  Can flow because their particles can move past each other  The only state that is not fluid is ______.

Buoyant Force  Upward force exerted on an object immersed or floating on a liquid.  All fluids exert pressure: the amount of force exerted per unit area of a surface.

Archimedes’ Principle  States that the buoyant force on an object IN the fluid is equal to the weight of the displaced volume of fluid.

 The volume of fluid displaced by an object placed in a fluid will be equal to the volume of the part of the object submerged.  The figure below shows how displacement works.

Density  Determines what floats and sinks If an object is _______dense than the fluid in which it is placed, it will float. If an object is more dense than the fluid in which it is placed, it will ______.

Practice Problems 1) What is the volume of a tank that can hold g of methanol whose density is 0.788g/cm 3 ? D = _______ m = _____ v = _____

2) What is the density of a board whose dimensions are 5.54 cm x 10.6 cm X 199 cm and whose mass is 28.6 g? D = _______ m = _____ v = _____

3) CaCl 2 is used as a de-icer on roads in the winter. It has a density of 2.50 g/cm 3. What is the mass of mL this substance? D = _______ m = _____ v = _____

Fluids and Pressure  Fluids exert pressure evenly in all directions. For example, when you pump up a bicycle tire, air particles are constantly pushing against each other and against the walls of the tire.

 Pressure can be calculated by dividing force by the area over which the force is exerted: ▪Pressure = Force Area  The SI unit for pressure is the pascal (abbreviation: Pa), equal to the force of one newton exerted over an area of one square meter (1 N/m 2 ).

Pascal’s Principle  States that a fluid in equilibrium enclosed by a vessel exerts pressure equally in all directions.  Mathematically, Pascal’s principle is stated as p 1 = p 2, or pressure 1 = pressure 2.

Math Skills  Pascal’s Principle A hydraulic lift, shown in the figure below, makes use of Pascal’s principle, to lift a 19,000 N car. If the area of the small piston (A 1 ) equals 10.5 cm 2 and the area of the large piston (A 2 ) equals 400 cm 2, what force needs to be exerted on the small piston to lift the car?

Math Skills, continued 1. List the given and unknown values. Given:F 2 = __________ N A 1 = __________ cm 2 A 2 = __________ cm 2 Unknown:F 1 2. Write the equation for Pascal’s principle. According to Pascal’s principle, p 1 = p 2.

 3. Insert the known values into the equation, and solve.  F1 = 500 N

Viscosity  Is a substance’s resistance to flow.  Which has the most viscosity? Water Honey Ketchup

Bernoulli’s Principle  Bernoulli’s principle states that as the speed of a moving fluid increases, the pressure of the moving fluid decreases.  Bernoulli’s principle is illustrated below: as a leaf passes through a drainage pipe from point 1 to point 2, it speeds up, and the water pressure decreases.