pressure
DESCRIPTION
GCSE Physics double award notesTRANSCRIPT
PressurePressure
GCSE PhysicsGCSE Physics
When else involves changes in pressure?
When is reduced pressure needed?
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
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
How important are feet?
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
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 = =
Extra QuestionsExtra Questions
Page 59Page 59 Questions 40, 42, 44, 46Questions 40, 42, 44, 46
Hydraulics Pg 59Hydraulics Pg 59
Some examples of Hydraulic Some examples of Hydraulic systems-systems-
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
Pressure remains the Pressure remains the same…same…
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.