Physicists are scientists who study forces. They learn all about why things act the way they do! This experiment will surprise you and your friends with how forces interact in ways that seem to defy gravity!
Materials:
Clear cup and strong paper (index card or construction paper works best).
Time Estimated:
5-10 minutes
Directions:
Note: It is best to do this outside or over a sink in case of a spill.
Fill the cup with water
Make sure the paper covers the entire rim of the cup and place on top. Cover with your hand and press firmly down with the palm of your hand.
Quick! Flip the cup upside down while pressing the paper on the rim and hold while you count to 5.
Take a deep breath and take off your hand! Surprise!
Think Like A Scientist!
Another scientist tried this and found that it is easier to complete the experiment if you press the paper firmly onto the rim of the cup. Remember to not break the paper! Trying new things and recording tips for other scientists is important in helping the whole scientific community learn more together! What tips did you figure out while doing the experiment?
What if you test with other liquids such as oil or juice? Do you get different results? Predict what might happen and then try it!
How it Works:
There are several forces involved in this experiment! The first force is atmospheric pressure. Atmospheric pressure pushes down on objects. It is caused by the weight of air (the atmosphere) pushing down on us!
In this experiment, the water in the glass pushes air out of the cup, so there is no air pressure inside the cup. Air particles can move freely, so the atmospheric pressure pushes on the cup from all directions, holding the paper in its place without water falling out of the cup!
The next force, gravity, is pulling down on the water. Gravity is why you stay standing on earth, and don’t float into outer space!
Surface tension of water creates something called adhesion to allow the paper to seal onto the cup. In addition, the last force, cohesion, allows polar molecules to hold onto each other. This means that the oxygen particles in the air--which are negatively charged--and the positive hydrogen ions in water creates cohesion.
Together, all of these forces help create the result that you see! The attractive force of the water and atmospheric pressure push up water and hold the paper in place!
Looking for more fun at home STEM activities for your young scientist? Check out our workbook full of exciting science experiments and empowering activities!
