1. Pressure

2. Tack pressing into wood vs finger
Knife cutting box
Side of knife vs edge
Tack pressing into wood vs finger
We can use the same force in two ways
Less concentrated – less pressure
More concentrated – more pressure

4. Pressure Force per unit area How concentrated the force is
P – Pressure (Pa or N/m2)
F – Force (N)
A – Area (m2)

5. Units for Pressure Pa – Pascal – a piece of newspaper lying on a desk
kPa – kilopascal - **
Psi – pounds per square inch - **
Atm – Atmosphere – pressure of air at sea level

6. Ex 1:
A car typically weighs about 2000kg. If a car has four wheels and each wheel makes contact with the ground over an area of approximately 20cm by 15cm, what pressure should the wheel be filled to?

7. Car Tire – 300 kPa or 44 psi

8. Atmospheric Pressure Created by the weight of air pushing down on us
100 kPa or 1 atm

9. Example 2
David sits on a toboggan. The dimensions of the sled touching the ground are 0.50m by 2.0m. If David’s mass is 70 kg, what is the pressure of the sled on the snow? Ans: 6.9x102Pa

10. Pressure Technology
Snow shoes

11. Iron Lung

12. Pg 228 # 1,3-5,7,8