Atmospheric Pressure: Qualitative Observational Experiment

Aim

Can we observe the effects of atmospheric pressure?

Prior Knowledge

1. Molecular structure of gases.
2. Newton's second Law, free body diagrams.
3. Physical quantity of pressure.
4. Model of static pressure in fluids.

Description of the Experiment

A glass is filled to the top with water. A piece of cardboard is placed over the top of the glass. The glass is then inverted

Observe what happens and try and explain what you see.

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Questions

1. What are the forces acting on the piece of cardboard?



2. Draw a free body diagram for the cardboard.



3. Which of the three forces acting on the cardboard is the largest? (Hint: to answer this question it is helpful to know that you can have a glass that is almost 10 m long to obtain the same results - the cardboard will stick. However, if it is taller than 10 m, the cardboard would fall off.)



4. How does this experiment demonstrate the effect of air pressure