1. Pressure
Chapter 43

2. Pressure Pressure is the force per unit area.
Pressure is measured in newtons per square metre (N/m2), or pascals (Pa). 1N/m2 = 1Pa.

3. Pressure in a Liquid Pressure increases with the depth of a liquid.
Pressure acts equally in all directions in a liquid.

4. Atmospheric Pressure
Atmospheric pressure is caused by the weight of the atmosphere.
Atmospheric pressure decreases the higher you go above sea level.

5. Measuring Pressure
A barometer can be used to measure atmospheric pressure.
Normal atmospheric pressure holds 76cm of mercury in a mercury barometer.
Normal atmospheric pressure is 76cm of mercury or 1013 hectopascals.

6. Mercury Barometer

7. Altimeter
An altimeter is a special barometer used to measure altitude.

8. The Weather and Pressure
High atmospheric pressure gives good, clear settled weather.
Low atmospheric pressure gives bad, wet unsettled weather.

9. To Demonstrate Atmospheric Pressure