The Power of Air
Have science fun as a family! Complete activities with parental supervision.
Materials:
- A large bowl of water
- Small clear cup that fits in the bowl
- A sheet of paper, paper towel or napkin
Procedure
- Fill the large bowl with water to about an inch from the top and place on a flat surface.
- Crumple up the paper or napkin and place it into the bottom of the cup. Flip the cup over to make sure it will stay in the cup and not fall out.
- Turn the cup upside down and lower it into the water. Keep the cup as straight as you can— make sure not to tilt it to one side or the other! Press firmly to keep it submerged and resting on the bottom of the bowl.
- If all went well, the water level around the cup should be higher than the paper. It looks like the paper is underwater! But is it wet?
- Slowly pull the cup straight up and out of the water. Be sure not to tilt the cup, even now.
- Check your paper. Is it wet? Or did it stay dry?
- If your paper came out wet, don’t worry—try it again! We don’t get things right the first time, so it’s important to try and try again!
- Keep trying this science trick and show it off to your family!
- Be sure to take a picture or video to share in the Facebook comments on the Buffalo Museum of Science or Tifft Nature Preserve pages!
What’s it all about?
This one is all about atmospheric pressure—the pressure exerted by the weight of the air in the atmosphere pushing down on everything. Atmospheric pressure is enormous (about 14.7 pounds per square inch!), but we barely notice it because it pushes on us from all directions.
The air inside the cup it at the same pressure as the air around it. When the cup is pushed into the water, the air molecules and the air pressure within it remain and acts as an air cushion. The trapped air cushion blocks the water from touching the paper and making it wet.
Try It!
- One way to experiment is to see how it can fail and figure out why it fails. Either when you place the cup into the bowl or take it out, tilt it slightly. What do you notice? Why does this make the trick fail?
