Objects don’t move, unless you add a force to act on them. That property of matter is called inertia. We’re able to decrease (make less) the force of friction acting on our objects enough that our cups didn’t move!
This activity explores the property of inertia and the forces of friction and gravity. When we remove the plate, our egg will fall (due to gravity), and stay in the same position relative to the cup (due to inertia).
The faster air flows over the surface of something, the less the air pushes on that surface (and so the lower its pressure). As gravity pulls the ball down, the air from the hair dryer flows around the outside of the ball while the pressure below the ball from the moving air forces it upward. When the forces are balanced, the ball hovers.
Materials:
How: Place a cup, plate or whole place setting on a tablecloth. Grab the tablecloth at the bottom and pull the tablecloth quickly down towards the ground (the direction that gravity is already pushing on them).
Pro Tip: Use a tablecloth that has little or no finished edge to reduce friction. Place the edge just behind your first cup, like in the video.
Experiment Further: Try different cloth textures, and objects of different masses and surface areas! Avoid using anything fragile that might break. As you practice you will make mistakes!
Materials:
How: Place plate on top of cup, with a paper tube above, and egg resting on top.
Reminder: The property of inertia will help us here. We want our egg to line up correctly so it sits directly above the cup opening. Hit the plate straight on, so that it is pushed out of the way creating an opening for the egg to fall into the cup.
Experiment Further: Try more – line up several of these in a row. How many can you do at once?
Materials:
How: Tape the cold button down on your hairdryer to keep things, cool. Plug in the hairdryer. Point the hairdryer towards the sky – so the air is blowing upwards. Place a ball in the stream of air.
Experiment Further: Try objects with different masses and surface areas! Explore how funneling air into a smaller area changes your experiment.
Partner with an Adult and try it with larger items – A leaf blower and a beachball!
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