Lesson 37: Pressure Inside and Outside
Pressure differences produce forces across surfaces and can drive the movement of fluids. Straws, breathing, and the middle ear provide examples of what happens when pressure differs inside and outside a space.
Key Ideas
- When air pressure is equal on both sides of a surface, the air pushes equally from both sides.
- When the pressures differ, the higher-pressure side pushes harder. This can move or bend a surface.
- Suction happens when pressure is lowered in one place. Higher pressure elsewhere can push air or water toward that place.
- Drinking through a straw lowers the pressure inside it. Air pressing on the drink’s surface helps push the liquid up the straw.
- A small passage connects your middle ear to the back of your nose and throat. It helps balance air pressure on the two sides of your eardrum.
Vocabulary
- Inside Pressure: The push of air inside a container or enclosed space.
- Outside Pressure: The push of air around the outside of a container or surface.
- Atmospheric Pressure: The push of the air around us. It acts in all directions.
- Equal Pressure: The same amount of air pressure on both sides of a surface.
- Unequal Pressure: Different air pressure on the two sides of a surface. One side pushes harder.
- Eustachian Tube: A small passage that helps balance air pressure on both sides of your eardrum.
Discussion Questions
- When you puff your cheeks out, what has changed about the air pressure inside your mouth compared to outside? What is doing the pushing?
- What happens to liquid flow if a juice container cannot admit replacement air? How might an opening change the pressure difference?
- Why does going down a hill or descending in an airplane often feel worse on the ears than going up?