# Pressure in Two Connected Bottles

## Objective

To clarify the concept of pressure in an interesting manner.

## Procedure

Make holes near the bottom of two bottles and connect them with a transparent pipe. Fill colored water in bottle 1 upto the 3/4 level and keep the bottle 2 empty. Close the cap of two bottles. Open the cap of bottle 2. Let atmospheric pressure be \(p_0\). Ask the following questions:

- Pressure of air in bottle 1 is (i) less than \(p_0\) (ii) more than \(p_0\) (iii) equal to \(p_0\)?
- Pressure of air in bottle 2 is (i) less than \(p_0\) (ii) more than \(p_0\) (iii) equal to \(p_0\)?
- If the cap of the bottle 1 is opened, what kind of water flow do you expect?
- No water will flow
- Some water will flow from bottle 1 to bottle 2
- Water will be equally divided in both bottles

## Discussion

The solution is:

- Bottle 1 is open. So pressure in it is \(p_0\). At the tube level pressure in bottle is also the same. As you go up in bottle 1 pressure decreases by \(h\rho g\). So pressure of air in bottle 1 is less than \(p_0\).
- \(p_0\) as it is open to atmosphere.
- Water will be equally divided in the two bottles.