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(Created page with "==Key Stage 4== ===Meaning=== Fluid Pressure is the force per unit area on a surface due to particles colliding with that surface. ===About Fluid Pres...")
 
 
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===Equation===
 
===Equation===
 +
''NB: You do not need to remember this equation.''
 +
 
Pressure = (Density of the Fluid) x (Gravitational Field Strength) x (Depth in the fluid)
 
Pressure = (Density of the Fluid) x (Gravitational Field Strength) x (Depth in the fluid)
  
 
<math> P = \rho g h</math>
 
<math> P = \rho g h</math>
  
−
Where:
+
Where
  
 
<math> P</math> = [[Pressure]] at that depth.
 
<math> P</math> = [[Pressure]] at that depth.
  
−
<math> \rho</math> = [[Density]] of the [[fluid]]
+
<math> \rho</math> = [[Density]] of the [[fluid]] (This symbol is a 'rho' not a 'p')
  
 
<math>  g </math> = [[Gravitational Field Strength]]
 
<math>  g </math> = [[Gravitational Field Strength]]
  
 
<math>h</math> = [[Depth]] in the [[fluid]]
 
<math>h</math> = [[Depth]] in the [[fluid]]
 +
 +
===Calculating Pressure in a Fluid===
 +
{| class="wikitable"
 +
| style="height:20px; width:200px; text-align:center;" |A whale dives to a depth of 1300m below sea level. Given the density of [[water]] is 1000kg/m<sup>3</sup>, calculate the [[pressure]] on the whale due to the water correct to two [[Significant Figures|significant figures]].
 +
| style="height:20px; width:200px; text-align:center;" |Normal atmospheric pressure at sea level is 101kPa. A miner works in a mine shaft 550m below the surface of the Earth. Given the density of the [[Earth's Atmosphere|atmosphere]] at this level is 1.2kg/m<sup>3</sup>, calculate the [[pressure]] on the miner correct to two [[Significant Figures|significant figures]].
 +
| style="height:20px; width:200px; text-align:center;" |A piece of [[Lithium]] is submersed 4.3cm deep in oil prevent it from oxidising. The oil has a [[density]] of 932kg/m<sup>3</sup>, calculate the [[pressure]] on the [[Lithium]] due to the oil correct to two [[Significant Figures|significant figures]].
 +
|-
 +
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
 +
 +
[[Density]] = 1000kg/m<sup>3</sup>
 +
 +
[[Gravitational Field Strength]] = 9.8N/kg
 +
 +
[[Depth]] = 1300
 +
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
 +
 +
[[Density]] = 1.2kg/m<sup>3</sup>
 +
 +
[[Gravitational Field Strength]] = 9.8N/kg
 +
 +
[[Depth]] = 550m
 +
| style="height:20px; width:200px; text-align:left;" |'''1. State the known quantities'''
 +
 +
[[Density]] = 932kg/m<sup>3</sup>
 +
 +
[[Gravitational Field Strength]] = 9.8N/kg
 +
 +
[[Depth]] = 4.3cm = 0.043m
 +
|-
 +
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
 +
 +
<math> P = \rho g h</math>
 +
 +
<math> P = 1000 \times 9.8 \times 1300</math>
 +
 +
<math> P = 12740000Pa</math>
 +
 +
<math> P \approx 13000000Pa</math>
 +
 +
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
 +
 +
<math> P = \rho g h</math>
 +
 +
<math> P = 1.2 \times 9.8 \times 550</math>
 +
 +
<math> P = 6468Pa</math>
 +
 +
Since the miner also has normal atmospheric pressure 101kPa is added.
 +
 +
<math> P_{Total} = 6468 + 101000</math>
 +
 +
<math> P_{Total} = 107468Pa</math>
 +
 +
<math> P_{Total} \approx 110000Pa</math>
 +
| style="height:20px; width:200px; text-align:left;" |'''2. [[Substitute (Maths)|Substitute]] the numbers into the [[equation]] and [[Solve (Maths)|solve]].'''
 +
 +
<math> P = \rho g h</math>
 +
 +
<math> P = 932 \times 9.8 \times 0.043</math>
 +
 +
<math> P = 392.7448Pa</math>
 +
 +
<math> P \approx 390Pa</math>
 +
|}
 +
 +
===References===
 +
====AQA====
 +
 +
:[https://www.amazon.co.uk/gp/product/1782945970/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782945970&linkCode=as2&tag=nrjc-21&linkId=a120d24dcc7cc7a58192069a3aafc1d2 ''Fluid pressure, pages 169-171, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA '']
 +
:[https://www.amazon.co.uk/gp/product/178294558X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=178294558X&linkCode=as2&tag=nrjc-21&linkId=f0dfb66dafcb0c6e9449e7b1a4ae1ac175 ''Fluid pressure, pages 58, 59, GCSE Physics; The Revision Guide, CGP, AQA '']
 +
 +
====Edexcel====
 +
 +
:[https://www.amazon.co.uk/gp/product/1782948163/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1782948163&linkCode=as2&tag=nrjc-21&linkId=0fdbfd5dd397d6e24a9dfb250f08587f ''Fluid pressure, pages 318, 319, GCSE Physics, CGP, Edexcel '']
 +
:[https://www.amazon.co.uk/gp/product/1292120223/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=1292120223&linkCode=as2&tag=nrjc-21&linkId=068ecf40278c32406a7f1c6e66751417 ''Fluids and pressure, pages 202-203, GCSE Physics, Pearson Edexcel '']

Latest revision as of 10:44, 20 November 2019

Key Stage 4

Meaning

Fluid Pressure is the force per unit area on a surface due to particles colliding with that surface.

About Fluid Pressure

The force responsible for pressure in a fluid is the weight of all the particles above the object.
The pressure in a fluid decreases with height and increases with depth. The deeper into a fluid the greater the pressure.
Since pressure increases with depth then the bottom of an object will experience more pressure than the top of the object. This causes a force called upthrust.

Equation

NB: You do not need to remember this equation.

Pressure = (Density of the Fluid) x (Gravitational Field Strength) x (Depth in the fluid)

\( P = \rho g h\)

Where

\( P\) = Pressure at that depth.

\( \rho\) = Density of the fluid (This symbol is a 'rho' not a 'p')

\( g \) = Gravitational Field Strength

\(h\) = Depth in the fluid

Calculating Pressure in a Fluid

A whale dives to a depth of 1300m below sea level. Given the density of water is 1000kg/m3, calculate the pressure on the whale due to the water correct to two significant figures. Normal atmospheric pressure at sea level is 101kPa. A miner works in a mine shaft 550m below the surface of the Earth. Given the density of the atmosphere at this level is 1.2kg/m3, calculate the pressure on the miner correct to two significant figures. A piece of Lithium is submersed 4.3cm deep in oil prevent it from oxidising. The oil has a density of 932kg/m3, calculate the pressure on the Lithium due to the oil correct to two significant figures.
1. State the known quantities

Density = 1000kg/m3

Gravitational Field Strength = 9.8N/kg

Depth = 1300

1. State the known quantities

Density = 1.2kg/m3

Gravitational Field Strength = 9.8N/kg

Depth = 550m

1. State the known quantities

Density = 932kg/m3

Gravitational Field Strength = 9.8N/kg

Depth = 4.3cm = 0.043m

2. Substitute the numbers into the equation and solve.

\( P = \rho g h\)

\( P = 1000 \times 9.8 \times 1300\)

\( P = 12740000Pa\)

\( P \approx 13000000Pa\)

2. Substitute the numbers into the equation and solve.

\( P = \rho g h\)

\( P = 1.2 \times 9.8 \times 550\)

\( P = 6468Pa\)

Since the miner also has normal atmospheric pressure 101kPa is added.

\( P_{Total} = 6468 + 101000\)

\( P_{Total} = 107468Pa\)

\( P_{Total} \approx 110000Pa\)

2. Substitute the numbers into the equation and solve.

\( P = \rho g h\)

\( P = 932 \times 9.8 \times 0.043\)

\( P = 392.7448Pa\)

\( P \approx 390Pa\)

References

AQA

Fluid pressure, pages 169-171, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Fluid pressure, pages 58, 59, GCSE Physics; The Revision Guide, CGP, AQA

Edexcel

Fluid pressure, pages 318, 319, GCSE Physics, CGP, Edexcel
Fluids and pressure, pages 202-203, GCSE Physics, Pearson Edexcel
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