pressure

15
Pressure Pressure GCSE Physics GCSE Physics

Upload: daniel-mcclelland

Post on 19-Jan-2015

2.897 views

Category:

Education


2 download

DESCRIPTION

GCSE Physics double award notes

TRANSCRIPT

Page 1: Pressure

PressurePressure

GCSE PhysicsGCSE Physics

Page 2: Pressure

When else involves changes in pressure?

Page 3: Pressure
Page 4: Pressure

When is reduced pressure needed?

Page 5: Pressure

PressurePressure Page 57Page 57 Pressure is how an applied Pressure is how an applied forceforce is is

distributed over andistributed over an area area (force per unit area) (force per unit area)

Pressure = Force / AreaPressure = Force / AreaNewton per metre squared = Newton / metre squaredNewton per metre squared = Newton / metre squared

N/mN/m22 = = NN // mm22

Another equivalent unit is used forAnother equivalent unit is used for N/m N/m22, the, the Pascal (Pa)Pascal (Pa)

P

F

A

Page 6: Pressure

Pressure ExamplesPressure Examples

Complete the table- Complete the table- (There are 10 000 cm(There are 10 000 cm22 in in 1 m1 m22))

PressurePressure ForceForce AreaArea

??

??

1000 Pa1000 Pa

500 N/m500 N/m22

10 N10 N

6.1 kN6.1 kN

200 N200 N

??

1 m1 m22

0.5 m0.5 m22

??

5000 5000 cmcm22

1.

2.

3.

4.

1.Pressure = Force / Area

P = 10 / 1 = 10 N/m2

10 N/m2

0.2 m2

250 N

12.2 kN/m2

Page 7: Pressure

How important are feet?

Page 8: Pressure

Surface area = 15 cm2

… And that is why

Elephingo or

Flamphants don’t exist!

Pressure = Force / Area

= 68 000 / 0.0015

= 45 333 333 N/m2

= 0.0015 m2

Page 9: Pressure

How much pressure are you How much pressure are you under?under?

What measurements do you need to take?What measurements do you need to take?

My mass =My mass =

My weight = My weight = ForceForce = =

Area of my shoe in contact with the ground Area of my shoe in contact with the ground ==

Total Total AreaArea = =

My Pressure = My Pressure = ForceForce / / AreaArea = =

Page 10: Pressure

Extra QuestionsExtra Questions

Page 59Page 59 Questions 40, 42, 44, 46Questions 40, 42, 44, 46

Page 11: Pressure
Page 12: Pressure

Hydraulics Pg 59Hydraulics Pg 59

Some examples of Hydraulic Some examples of Hydraulic systems-systems-

Page 13: Pressure

Pascal PrinciplePascal Principle

Liquids Liquids cannot be compressedcannot be compressed and and the pressure is the pressure is transmitted equallytransmitted equally throughout.throughout.

Small Force

applied to Master piston

BIG resultant force

at Slave piston

Liquid

Volume remains the same, not squishy

Page 14: Pressure

Pressure remains the Pressure remains the same…same…

Page 15: Pressure

Pascal PrinciplePascal Principle

The pressure is transmitted The pressure is transmitted equallyequally in in the liquid. This means the force the liquid. This means the force applied at the applied at the master pistonmaster piston is is MULTIPLIED UP when transferred to MULTIPLIED UP when transferred to the the slave pistonslave piston..

The slave piston has a The slave piston has a greater areagreater area than the master piston. than the master piston.

Therefore the force must be Therefore the force must be increasedincreased at the slave piston to keep the at the slave piston to keep the pressure constant.pressure constant.