Examples of air exerts down ward pressure?

Answer 1

1. Put a little water (about 20 ml) in the flask and heat it to a boil.

2. Let the water boil vigorously for at least one full minute.

3. Take the flask off the hot plate and immediately place the balloon with the mouth over the flask's mouth.

4. Let cool slowly at room temperature (the balloon will be pushed inside out into the flask).