Pressure
• Force per unit area
• How concentrated the force is
F
P
A
P – Pressure (Pa or N/m2)
F – Force (N)
A – Area (m2)
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
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?
Car Tire – 300 kPa or 44 psi
Atmospheric Pressure
• Created by the weight of air pushing down on us
• 100 kPa or 1 atm
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