Pressure Calculation and Comparison Guide
Learn how to convert units, calculate pressure, and compare pressure values. Understand why it's essential to have consistent units for pressure comparison. Explore scenarios like an elephant stepping on your toe vs. the heel of a shoe in terms of pressure exerted.
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Presentation Transcript
Skills needed for today: ? Convert 3m into cm ? Convert 3cm into m ? From last term: What is the value of ??? 30? From last year: What is the midpoint of (7,9) and (13,1)?
Mark your work 3? = 300?? 3?? = 0.03? 3 cos30 = 2 (10, 5)
Which would hurt more? An elephant stepping on your toe or the heel of this ladies shoe?
With more information we could calculate which would be most painful Exerts force of 60 000 ??????? on the ground with each step Exerts force of 500 ??????? on the ground with each step Area of foot is approximately 0.12?2 Area of heel of shoe is approximately 1??2 With this information we could calculate and compare the pressure exerted.
A commonly used unit of pressure is ?/?2 What is the formula for pressure? ???????? =????? N ???? m2
Calculating Pressure Exerts force of 60 000 ??????? on the ground with each step Exerts force of 500 ??????? on the ground with each step Area of foot is approximately 0.12 ?2 Area of heel of shoe is approximately 1 ??2 60000 0.12 500 1 = 500,000 N/?2 = 500 N/??2 ???????? = ???????? = Why can these values for pressure NOT be compared?
Calculating Pressure Exerts force of 60 000 ??????? on the ground with each step Exerts force of 500 ??????? on the ground with each step Area of foot is approximately 0.12 ?2 Area of heel of shoe is approximately 1 ??2 60000 0.12 500 1 = 500,000 N/?2 = 500 N/??2 ???????? = ???????? = The units must be the same for the pressures to be compared.
Calculating Pressure Exerts force of 500 ??????? on the ground with each step 1 ??2 1?? 0.01? ? Area of heel of shoe is approximately 1 ??2 1?? 0.01? ? 1??2= 0.012= 0.0001?2 500 0.0001= 5,000,000 N/?2 ???????? =
Calculating Pressure Exerts force of 60 000 ??????? on the ground with each step Exerts force of 500 ??????? on the ground with each step Area of foot is approximately 0.12 ?2 Area of heel of shoe is approximately 0.0001 ?2 60000 0.12 500 0.0001= 5,000,000 N/?2 = 500,000 N/?2 ???????? = ???????? = .
Which would hurt more? The heel of this dancers shoe exerts 10 times the pressure of the elephants foot.
1??2= 0.012= 0.0001?2 1 ??2 1?? 1002 0.01? 9 ??2= 0.032= 0.0009?2 9 ??2 1002 3 ?? 0.03? In general, ??2 1002 ?2
1 ?2=1002= 10000 ?2 1 ?2 1 ? 1002 100 ?? 25 ?2= 5002= 250000 ??2 25 ?2 1002 5 ? 500 ?? In general, ?2 1002 ??2
The force exerted by a bottle of water on table is 5N. The area of the bottom of the bottle is 9??2 On your whiteboards, work out the pressure exerted by the pencil on to the paper in ?/??2. 5 9= 0. 5 ?/??2 ???????? =
The force exerted by a bottle of water on table is 5N. The area of the bottom of the bottle is 9??2 On your whiteboards, work out the pressure exerted by the pencil on to the paper in ?/?2. 9 ??2= 0.032= 0.0009?2 9 ??2 3 ?? 5 0.0009= 5555. 5 ?/??2 0.03? ???????? = 3 ?? 0.03?
The force exerted by a car on a road is 5000N. The area of the tyres in contact with the road has a total of 25?2 On your whiteboards, work out the pressure exerted by the pencil on to the paper in ?/?2. 5000 25 = 200 ?/?2 ???????? =
The force exerted by a car on a road is 5000N. The area of the tyres in contact with the road has a total of 25?2 On your whiteboards, work out the pressure exerted by the pencil on to the paper in ?/??2. 25?2= 500 500 = 250,000??2 25 ?2 5? 5000 250000= 0.02 ?/??2 500 ?? ???????? = 5? 500 ??
Title: Pressure Pressure can be calculated by dividing the force exerted by an object by its area. Commonly used units for pressure are ?/?2and ?/??2. To convert ??2to ?2 divide by 1002 To convert ?2 to ??2 multiply by 1002
Your turn: 1. Convert these areas to ?2 (a) 40 000 ??2 (b) 80 000 ??2 (c) 1 000 000 ??2 (d) 125 000 ??2 (e) 5000 ??2 3. Calculate the pressure exerted in ?/?2 (a) Force 13 N, Area 10 ?2 (b) Force 480 N, Area 25 ??2 4. Calculate the pressure exerted in ?/??2 (a) Force 480 N, Area 25 ??2 (b) Force 13 N, Area 10 ?2 2. Convert these areas to ??2 (a) 5 ?2 (b) 10 ?2 (c) 6.5 ?2 (d) 7.75 ?2 (e) 0.6 ?2 5. Convert these pressures: ?/??2 10.2 1.6 ?/?2 Air Blood Tyre Tap Water 4.7 105 5 105
Mark your work 1. Convert these areas to ?2 (a) 40 000 ??2 4 (b) 80 000 ??2 8 (c) 1 000 000 ??2 100 (d) 125 000 ??2 12.5 (e) 5000 ??2 0.5 3. Calculate the pressure exerted in ?/?2 (a) Force 13 N, Area 10 ?2 1.3 (b) Force 480 N, Area 25 ??2192 000 4. Calculate the pressure exerted in ?/??2 (a) Force 480 N, Area 25 ??2 19.2 (b) Force 13 N, Area 10 ?2 0.00013 2. Convert these areas to ??2 (a) 5 ?2 50 000 (b) 10 ?2 100 000 (c) 6.5 ?2 65 000 (d) 7.75 ?2 775 000 (e) 0.6 ?2 6000 5. Convert these pressures: ?/??2 10.2 1.6 47 50 ?/?2 102000 16000 4.7 105 5 105 Air Blood Tyre Tap Water
Challenge The force exerted by a block of wood is 7N, correct to the nearest integer. The area of the wood in contact with a surface is 42??2, correct to 2 significant figures. Work out the smallest possible pressure in ?/?2 exerted by the block on the surface. Give your answer to 3 significant figures.
