Pressure.

Slides:



Advertisements
Similar presentations
Pressure.
Advertisements

L 13 Fluids [2]: Statics  fluids at rest
Pressure and Pivots Pressure P = F / A Fluid pressure P = ρ g h
Pressure. What is Pressure? “Amount of force exerted on an area” Earth’s gravity pulls downward Due to gravity, your feet exert a force on the surface.
D. Crowley, To be able to explain how gases and liquids exert pressure Tuesday, May 19, 2015.
L12 - FLUIDS-1 liquids gases sand, snow, or grain (granular materials) FLUIDS  STUFF THAT FLOWS FLUIDS 1.
Existence of Gas pressure based on the kinetic theory gas molecules move freely and randomly. The gas molecules collide with one another and also collide.
L12- FLUIDS [1]  liquids  gases  sand Matter  Comes in three states – solid, liquid, gas  So far we have only dealt with solid objects  blocks,
Pressure in Fluid Systems
Chapter 12: Forces and Fluids
Higher Physics – Unit – Density and Pressure.
Pgs  Calculate the pressure exerted by a fluid.  Explain Pascal’s Principle.  Calculate how pressure varies with depth in a fluid.
Lesson 2 Pressure.
PRESSURE OF A FLUID Barometer air pressure pressure = height of mercury column.
Physical Science Unit: Forces in Fluids.
Pressure; Pascal’s Principle
Forces and Fluids. What is a fluid? A fluid is any material that can flow and take the shape of its container. A fluid can flow because its particles.
Forces and Fluids.
PRESSURE Presented by: Catherine G.Tumaliuan Novaliches High School Quezon City,Philippines April 12,2010.
* Pressure refers to a force pushing on a surface * Force and pressure are closely related, but are not the same thing * Pressure deals with force and.
Chapter 10 Fluids. Units of Chapter 10 Phases of Matter Density Pressure in Fluids Atmospheric Pressure and Gauge Pressure Pascal’s Principle Measurement.
L 13 Fluids [2]: Statics  fluids at rest  More on fluids.  How can a steel boat float.  A ship can float in a cup of water!  Today’s weather Today’s.
Fluids and Motion Pressure – Refers to a force pushing on a surface. Area is the measure of a surface. Calculating Pressure – Pressure (Pa) = Force (N)
L 13 Fluids [2]: Statics  fluids at rest  More on fluids at rest  How is atmospheric pressure measured?  Buoyancy: How can a steel boat float?
Pressure and Fluids § 12.1–12.3. Density Relating “how big” to “how much” § 12.1.
L 13 Fluids [2]: Statics  fluids at rest  More on fluids.  How can a steel boat float.  A ship can float in a cup of water!  Today’s weather Today’s.
Forces and Fluids.
Pressure.
Unit 7: Pressure MC Textbook Chp 7 GLM Red Book Chp 6.
Stuff that Flows L12- FLUIDS-1 liquids gases
Objectives  Know the relationship between pressure, force and area.  Know the relationship between fluid pressure, density and height (or depth) of.
Pressure in solids, liquids Atmospheric pressure
L 13 Fluids [2]: Statics  fluids at rest  More on fluids.  How can a steel boat float.  A ship can float in a cup of water!  Today’s weather Today’s.
Chapter 1.2 Notes Pressure. All matter is made up of atoms and molecules. All matter is made up of atoms and molecules. Matter can exist in four states:
Forces and Fluids Chapter 12 BIG IDEAS Newton’s laws apply to all forces Gravity is a force exerted by all masses Friction is a force that opposes motion.
PHYSICS – Pressure. LEARNING OBJECTIVES 1.8 Pressure Core Recall and use the equation p = F / A Relate pressure to force and area, using appropriate examples.
L 13 Fluids [2]: Fluid Statics  fluids at rest  More on fluids at rest  How is atmospheric pressure measured?  Buoyancy: How can a steel boat float?
L 13 Fluids - 2 Fluid Statics: fluids at rest
L 13 Fluids [2]: Statics  fluids at rest  More on fluids at rest  How is atmospheric pressure measured?  Today’s weather Today’s weather Today’s weather.
Pressure. What is Pressure? Pressure refers to a force exerted on a surface Due to the force of gravity, your feet exert a force on the ground in the.
Chapter 10 Fluids Pressure in Fluids Pressure is defined as the force per unit area. Pressure is a scalar; the units of pressure in the SI system.
FORCES IN FLUIDS CHAPTER 11. Section 11-1 Pressure Pressure - related to the word press - refers to the force pushing on a surface.
Chapter 12: Forces and Fluids
L 13 Fluids [2]: Statics  fluids at rest
L 13 Fluids [2]: Fluid Statics: fluids at rest
Pressure in Solids.
Pressure.
Static Fluids Fluid – any substance that takes the form of the container in which it is held. (gases and liquids)
Fluids can exert a force on objects
What will happen – Why? When the barrier is removed, what will happen and can you explain why?
Forces in Fluids Pressure.
Columns of fluid Density Pressure Pressure variation with depth
Questions 1. A car travels 240 km in 8 hours. What is its speed?
PHYSICS – Pressure.
Module 1 FORCE.
Pressure.
Physical Science Forces in Fluids.
What would be more painful?
Chapter 12 Section 1.
Pressure.
Hydraulics Noadswood Science, 2013.
L 13 Fluids [2]: Statics  fluids at rest
Section 3 – pg 432 Pascal’s Principle
IGCSE Physics Pressure.
IGCSE Physics Pressure.
Chapter 11 Section 1 – pg 416 Pressure.
FORCES IN FLUIDS CHAPTER 11.
L 13 Fluids [2]: Statics  fluids at rest
Presentation transcript:

Pressure

Pressure in solids An elephant will exert less pressure than a person wearing high heels. This is because the weight of the elephant is spread over a larger surface area. Sir jumps quickly to his feet He’s got the point (-he’s got a scar!) The pressure acting on his seat, Is force per unit areaaaaaaaaagh!

Pressure is Force per Unit Area Force ÷ Area = Pressure Measured in N/m2 or N/cm2 N/m2 = 1Pa (pascal)

Pressure in solids This man can lie on a bed of nails because by having many nails he has increased the surface area so his pressure is less.

Reducing Pressure These are all examples of where pressure in reduced by increasing surface area

Increasing pressure

Pressure in solids It acts in the direction of the force only. The smaller the area the higher the pressure. The larger the area the smaller the pressure

Calculating pressure

Pressure in liquids

Pressure in liquids at depth Pressure in liquids acts in all directions. The greater the depth the greater the pressure, as the mass (and therefore the force exerted) is greater.

Pressure is exerted throughout the liquid and in all directions. The deeper the water the greater the pressure because the weight of the water is greater

Calculating pressure at depth Pressure = 10 x depth x density (N/m2 ) ( N/kg) (m) (kg/m3) The hydrometer This is used to measure the density of milk and other liquids. It floats to different depths in different liquids, depending on their densities

Upthrust and Pressure All liquids exert an upthrust because the pressure inside the liquid increases as you go deeper. This means that the pressure on the bottom of an object is greater than on the top, and so there is a resultant force upwards

Pressure in liquids Liquids will find their own level

Pressure in Liquids Higher density higher pressure.

Using pressure in liquids Hydraulic machines It was easier to push on the small syringe that on the big syringe. This is because a force acting over small area creates a high pressure. This pressure is then transmitted through the fluid and acts over a large area. This results in a larger force on the plunger of the large syringe.

Using pressure in liquids

The drivers foot pushes the piston to exert pressure on the liquid The drivers foot pushes the piston to exert pressure on the liquid. This pressure is transmitted to the pistons on each side of the large disc on the axle. The pressure makes the pistons squeeze the disc like the brakes on a bicycle to slow down the car. Exactly the same pressure is applied to the other brakes on the car. If the pistons have twice the area of the master piston, they will exert twice the force that the driver applied with her foot. The force is magnified by the increased area of the pistons.

Using Pressure in Liquids The moving arms on this mechanical digger use hydraulic systems

Hydraulic Jack

Pressure in Gases We are living at the bottom of a ‘sea’ of air called the atmosphere, which exerts a pressure on us (just as the sea squeezes a diver). Atmospheric pressure is 100 000N/m2

Collapsing Can Experiment Before the pump is switched on, molecules are hitting the outside and inside with equal pressure. After the pump is switched on, there are almost no molecules inside the can and the pressure of the molecules outside the can crushes it.

Gases can be Compressed ...Pressure increases

Exploding Marshmallow At first the atmospheric pressure on the outside of the balloon balances the air pressure inside ....

...when you pump out the air A vacuum is created in the bell jar air pressure in the balloon / marshmallow is higher than the pressure in the bell jar so the balloon expands

Using pressure Sucking creates a negative pressure in the straw. The high air pressure acting on the surface of the liquid pushes the liquid up the straw.

Using Air Pressure The higher pressure outside the sucker holds it in place. As you push the sucker down air is forced out of the cup creating a negative pressure

Measuring Pressure Bourdon Gauge: The higher pressure makes the tube straighten out slightly, and this movement is used to turn a pointer

Measuring Pressure Aneroid Barometer: This uses a flexible metal can which has had the air taken out of it. A strong spring stops the atmosphere from completely crushing the can. If the air pressure increases, the top of the can is squeezed down slightly. If the air pressure decreases, the spring pulls up the top of the can. This small movement is magnified by a long pointer

Measuring Pressure The Mercury Barometer: The column of mercury is held up by air pressure. As the air pressure varies from day to day (depending on the weather), the height of the Mercury varies. The distance to measure is shown in the diagram. A height of 760 mm is called Standard Atmospheric Pressure

PRESSURE SUMMARY Pressure is the force per unit area It is measured in N/m2 ( Pascals), N/cm2 , Bar. The larger the area the more the force is spread so the less the pressure. The smaller the area the less the force is spread, so the greater the pressure. In liquids and gases the fluids will flow from an area of high pressure to an area of low pressure until the pressure is equal throughout. Pressure in a liquid is greater at depth. Pressure in liquids and gases are exerted equally throughout. The same pressure at equal depths.