Review; Ch. 3•Boyle’s Law; When the pressure of a fluid atconstant temperature is increased, the volume of fluiddecreases, when the pressure is decreased, thevolume increases.•Charle’s Law; When the temperature of a fluidincreases at constant pressure, its volume increases.When the temperature decreases its volumedecreases.
Pressure•Pressure is a “pressing” force; a push.•Pressure depends on the amount of area over which itis exerted.•Pressure = Force/Area (add to circle formula sheet).•Units: Newtons/Meters2•which is called “Pascals”•Also measured in atm,•mmHg, etc.
Fluid Pressure•Gas or Liquid•“In a fluid the molecules exert anequal pressure in all directions”.•We live at the bottom of 100km offluid air which exerts a pressure of14.7 lbs/square inch.•This pressure is exerted equally inall directions: up and down and is saidto be “balanced”.•Unbalanced forces produce motion
Fluid Pressure, cont.•Air pressure decreases with altitude.•Liquid pressure increases with depth below surface.•Air pressure is measured with a barometer.•Liquid pressure is measured with a hydrometer.
Density & Buoyant•Density is mass/volume•D = M/V; write circle formula on sheet if not there.•Water is one: Density of water = 1g/cm .3•One gram per cubic centimeter.•
Predicting Floating & Sinking•Knowing that water is one you can predict if anobject will float or sink•Less than one will float, more than one will sink.• D = m/v.•Density will increase if Mass increases or Volumedecreases.•Density will decrease if Mass decreases or Volumeincreases.
Buoyancy•The buoyant force acts in adirection opposite to gravity tomake an have less weight but thesame mass.•Weight < buoyancy = floats•Weight > buoyancy = sinks•Weight = buoyancy = hovers
Archimedes’ Principle•The buoyant force acting up on a submerged object isequal to the force of the weight of the volume of liquid theobject displaces.•
Archimedes’ Principle•When the weight of the water displaced by theobject equals the buoyant force on the object, it willfloat.
Conversions•Newtons = grams times 0.01N/g (for Archimedes’lab p. 430)•
Pascal’s Principle•When force is applied to a confined fluid, the changein pressure is transmitted equally in all directions to allparts of the fluid.