1. Skills needed for today: Convert 3m into cm Convert 3cm into m𝟑 𝟐 𝟏
From last term:
What is the value of 𝑐𝑜𝑠 30?
From last year:
What is the midpoint of (7,9) and (13,1)?
Timed spaced retrieval – non calculator

2. Mark your work
3𝑚=300𝑐𝑚 3𝑐𝑚=0.03𝑚 cos 30= 3 2 (10, 5)

3. Which would hurt more? An elephant stepping on your toe
or the heel of this ladies shoe?

4. With more information we could calculate which would be most painful…
Exerts force of 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of foot is approximately 0.12 𝑚 2
Exerts force of 500 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of heel of shoe is approximately 1 𝑐𝑚 2
With this information we could calculate and compare the pressure exerted.

5. 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 𝐹𝑜𝑟𝑐𝑒 𝐴𝑟𝑒𝑎 What is the formula for pressure? N m2
A commonly used unit of pressure is 𝑁/ 𝑚 2
What is the formula for pressure?
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 𝐹𝑜𝑟𝑐𝑒 𝐴𝑟𝑒𝑎 N m2

6. Calculating Pressure 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 60000 0.12 =500,000 N/ 𝑚 2
Exerts force of 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of foot is approximately 𝑚 2
Exerts force of 500 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of heel of shoe is approximately 1 𝑐𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =500,000 N/ 𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =500 N/ 𝑐𝑚 2
Why can these values for pressure NOT be compared?

7. The units must be the same for the pressures to be compared.
Calculating Pressure
Exerts force of 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of foot is approximately 𝑚 2
Exerts force of 500 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of heel of shoe is approximately 1 𝑐𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =500,000 N/ 𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =500 N/ 𝑐𝑚 2
The units must be the same for the pressures to be compared.

8. Calculating Pressure 1 𝑐𝑚 2 1𝑐𝑚 ? 0.01𝑚 1𝑐𝑚 ? 0.01𝑚
Exerts force of 500 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of heel of shoe is approximately 1 𝑐𝑚 2
1 𝑐𝑚 2
1𝑐𝑚 ?
0.01𝑚
1𝑐𝑚 ?
0.01𝑚
1𝑐 𝑚 2 = = 𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =5,000,000 N/ 𝑚 2

9. Calculating Pressure 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 60000 0.12 =500,000 N/ 𝑚 2
Exerts force of 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of foot is approximately 𝑚 2
Exerts force of 500 𝑛𝑒𝑤𝑡𝑜𝑛𝑠 on the ground with each step
Area of heel of shoe is approximately 𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =500,000 N/ 𝑚 2
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =5,000,000 N/ 𝑚 2 .

10. Which would hurt more?
The heel of this dancers shoe exerts 10 times the pressure of the elephants foot.

11. 1 𝑐𝑚 2
1𝑐 𝑚 2 = = 𝑚 2
1𝑐𝑚
÷ 100 2
0.01𝑚
9 𝑐𝑚 2
9 𝑐𝑚 2 = = 𝑚 2
÷ 100 2
3 𝑐𝑚
0.03𝑚
In general, 𝑐𝑚 2 →÷ → 𝑚 2

12. 1 𝑚 2
1 𝑚 2 = = 𝑚 2
1 𝑚
× 100 2
100 𝑐𝑚
25 𝑚 2
25 𝑚 2 = = 𝑐 𝑚 2
× 100 2
5 𝑚
500 𝑐𝑚
In general, 𝑚 2 →× → 𝑐𝑚 2

13. The force exerted by a bottle of water on table is 5N
The force exerted by a bottle of water on table is 5N. The area of the bottom of the bottle is 9 𝑐𝑚 2
On your whiteboards, work out the pressure exerted by the pencil on to the paper in 𝑁/ 𝑐𝑚 2 .
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 5 9 =0. 5 𝑁/ 𝑐𝑚 2
Share and compare different methods on student whiteboards

14. The force exerted by a bottle of water on table is 5N
The force exerted by a bottle of water on table is 5N. The area of the bottom of the bottle is 9 𝑐𝑚 2
On your whiteboards, work out the pressure exerted by the pencil on to the paper in 𝑁/ 𝑚 2 .
9 𝑐𝑚 2
9 𝑐𝑚 2 = = 𝑚 2
3 𝑐𝑚
Share and compare different methods on student whiteboards
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= = 𝑁/ 𝑐𝑚 2
0.03𝑚
3 𝑐𝑚
0.03𝑚

15. The force exerted by a car on a road is 5000N
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 𝑚 2
On your whiteboards, work out the pressure exerted by the pencil on to the paper in 𝑁/ 𝑚 2 .
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =200 𝑁/ 𝑚 2
Share and compare different methods on student whiteboards

16. The force exerted by a car on a road is 5000N
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 𝑚 2
On your whiteboards, work out the pressure exerted by the pencil on to the paper in 𝑁/ 𝑐𝑚 2 .
25 𝑚 2
25 𝑚 2 =500×500=250,000 𝑐𝑚 2 5𝑚
Share and compare different methods on student whiteboards
500 𝑐𝑚
𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= =0.02 𝑁/ 𝑐𝑚 2 5𝑚
500 𝑐𝑚

17. Title: Pressure
Pressure can be calculated by dividing the force exerted by an object by its area. Commonly used units for pressure are 𝑁/ 𝑚 2 and 𝑁/ 𝑐𝑚 2 . To convert 𝑐𝑚 2 to 𝑚 2 divide by To convert 𝑚 2 to 𝑐𝑚 2 multiply by 100 2

18. Your turn:
Convert these areas to 𝑚 2
𝑐𝑚 2
𝑐𝑚 2
𝑐𝑚 2
𝑐𝑚 2
5000 𝑐𝑚 2
2. Convert these areas to 𝑐𝑚 2
5 𝑚 2
10 𝑚 2
6.5 𝑚 2
7.75 𝑚 2
0.6 𝑚 2
3. Calculate the pressure exerted in 𝑁/ 𝑚 2
Force 13 N, Area 10 𝑚 2
Force 480 N, Area 25 𝑐𝑚 2
4. Calculate the pressure exerted in 𝑁/ 𝑐𝑚 2
5. Convert these pressures:
𝑁/ 𝑐𝑚 2
𝑁/ 𝑚 2
Air
10.2
Blood
1.6
Tyre
4.7× 10 5
Tap Water
5× 10 5

19. Mark your work
Convert these areas to 𝑚 2
𝑐𝑚 2 4
𝑐𝑚 2 8 𝑐𝑚 𝑐𝑚
5000 𝑐𝑚
2. Convert these areas to 𝑐𝑚 2
5 𝑚
10 𝑚
6.5 𝑚
7.75 𝑚
0.6 𝑚
3. Calculate the pressure exerted in 𝑁/ 𝑚 2
Force 13 N, Area 10 𝑚
Force 480 N, Area 25 𝑐𝑚
4. Calculate the pressure exerted in 𝑁/ 𝑐𝑚 2
Force 480 N, Area 25 𝑐𝑚
Force 13 N, Area 10 𝑚
5. Convert these pressures:
𝑁/ 𝑐𝑚 2
𝑁/ 𝑚 2
Air
10.2
102000
Blood
1.6
16000
Tyre 47
4.7× 10 5
Tap Water 50
5× 10 5

20. 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 𝑐𝑚 2 , correct to 2 significant figures. Work out the smallest possible pressure in 𝑁/ 𝑚 2 exerted by the block on the surface. Give your answer to 3 significant figures.
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