Forces influence the motion and properties of fluids

FORCES AND BUOYANCY Section 9.1Page 333

Anything that causes a change in the motion of an object.

 Are EQUAL in Strength  OPPOSITE in DIRECTION  Result in NO movement

 Are UNEQUAL in Strength  Cause a CHANGE in SPEED or DIRECTION

MASS vs WEIGHT SONG SONG Amount of matter in a substance A measure of the push or pull acting on an object Stays the same anywhere in the Universe Will change as gravitational forces change Measured in grams (g) or kilograms (kg) 1kg=1000g Newton (N) 1 N = 100g

MASS versus WEIGHT

The upward force on an object submerged in or floating on fluids. An object that floats has a neutral buoyancy

Sink or Float ? An object will float if it’s buoyant force is greater than its weight (gravitational force) An object will sink if it’s buoyant force is less than its weight

ARCHIMEDES’ PRINCIPLE VIDEO The buoyant force acting on an object equals the weight of the fluid displaced by the object VIDEO

Technologies invented based on buoyancy and density Life jackets and PFD Submarines Hot air balloons

DENSITY AND BUOYANCY  If the density of the immersed object is greater than the density of the fluid it will SINK  If the density of the immersed object is less than that of the fluid it will FLOAT

AVERAGE DENSITY VIDEO

QUESTIONS #1-10 AND PAUSE AND REFLECT Check your UnderstandingPage 347

PRESSURE, HYDRAULICS AND PNEUMATICS Section 9.2Page 348

The force acting on a certain area of surface The LARGER the force the greater the pressure The smaller the area the greater the pressure

CALCULATING PRESSURE  The unit for pressure is the Pascal (Pa)  You can determine pressure if you know the FORCE and AREA VIDEO

FORMULA: F= P x A P = F A A = F P F P A F = Force (N) P = Pressure (Pa) A = Area (m 2 )

SAMPLE PROBLEM 1: FINDING P  An aquarium is filled with water that weighs N. If the base of the aquarium has an area of 1.6 m 2, what pressure does the water exert on its base?  F = N P = ? A = 1.6 m 2 P = F A P = N 1.6 m 2 P = 6250 Pa

SAMPLE PROBLEM 2: FINDING F  If the atmospheric pressure is Pa and you are holding your hand, the atmosphere is exerting a force on your hand. If the area of your palm is m 2, calculate the force on your hand.  F = ? P = Pa A = m 2 F = P x A F = ( Pa)(0.006m 2 ) F = 607 N

SAMPLE PROBLEM 3: FINDING A  The weight of water in a glass is 4.9 N. If the water is exerting a pressure of 1700 Pa on the bottom of the glass, what is the areas of the bottom of the glass?  F = 4.9 N P = 1700 Pa A = ? A = F P A = 4.9 N 1700 Pa A = m 2

COMPRESSIBILITY - the ability to be squeezed into a smaller volume or space.  There are large spaces between the particles in gases.  They have an indefinite volume and can be COMPRESSED.  There is less space between the particles of liquids.  They have a definite volume and are INCOMPRESSIBLE. GASES LIQUIDS

ATMOSPHERIC PRESSURE  The amount of force that is exerted by the weight of the atmosphere.  The atmosphere is the layer of air that surrounds the earth. (~160 km)  There is less atmospheric pressure at higher altitudes.

PASCAL’S LAW The pressure applied to an enclosed fluid is transmitted with equal force throughout the entire container. This is the basis for HYDRAULIC and PNEUMATIC devices.

HYDRAULICS  The study of pressure in LIQUIDS  Liquids are contained within a tube and when a force is applied at one end, the other moves.  Examples: car lift, hydraulic jack, breaking system  The study of pressure in GASES  Compressors are used to build up air pressure  Examples: air compressors and bicycle tires PNEUMATICS

QUESTIONS #1-9 Check your Understanding Page 363

Relationships Among P, V and T of Gases Section 9.3Page 364

THE 3 GAS LAWS  BOYLE’S LAW – Pressure and Volume  CHARLES’S LAW – Temperature and Volume  GAY-LUSSAC’S LAW – Temperature and Pressure

PRESSURE and VOLUME BOYLE’S LAW INCREASING the pressure on a fluid will decrease the volume by the same amount. VIDEO VIDEO 2

TEMPERATURE and VOLUME CHARLES’S LAW INCREASING the temperature on a fluid will INCREASE the volume of a fluid. VIDEO

TEMPERATURE and PRESSURE GAY-LUSSAC’S LAW INCREASING the temperature of a fluid will INCREASE the pressure. VIDEO

QUESTIONS #1,3,5,8,10 Check your Understanding Page amazing science tricks using fluids