28 Jan STEM Challenge – Defying Gravity Challenge
In the coming weeks you are going to be learning about gravity! When you drop an object from your hand, what happens to that object? It falls to the ground! If you have a glass of water and you turn it upside down, what happens? The water falls out of the glass and spills onto the floor. What makes this happen? Gravity.
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What is Gravity?
Gravity is the force that pulls matter toward the Earth. It is why objects fall to the ground when dropped and why when you jump into the air, you come right back down. In this experiment we are going to try and defy gravity to make something that normally falls to the ground not fall.
- Large bowl of water
- Baking tray or other tray for easy clean-up.
- Small clear glass or cup
- Food coloring (optional)
- To set up this experiment, fill your large bowl with water, almost to the top, add some food coloring, and mix it well. The color is optional but it will make it easier to see the experiment in action. You can place your large bowl of water on top of a baking tray just in case some water spills over during the experiment.
- Next, place your small glass in the bowl of water so that the glass fills with water (the bottom of the glass should be resting at the bottom of the bowl). Ideally, you want the glass fully submerged or covered with the water (it is okay if your glass is sticking out of the water a tiny bit, the experiment will still work just fine).
- While keeping the small glass under the water as much as possible, turn the glass upside down in the bowl. The glass should be full of water with no air.
- Carefully lift the glass until the top rim of the glass is just below the surface of the water. Notice that the water is still in the glass and isn’t falling back into the bowl. The water seems to defy gravity.
- Lift the glass fully above the surface of the water. What happens to the water in the glass?
The Science Behind the Experiment:
There are two forces at play in this experiment – gravity and air pressure. Gravity is always pulling objects to the Earth. The same is happening with the water in the glass. When you begin to lift the glass out of the water, gravity is trying to pull the water to the Earth and out of the glass.
Air pressure is also always at work, constantly pushing on objects. In this case, it is pushing down on the water around the glass. This pressure is enough to temporarily defy the force of gravity on the water in the glass, and so the water stays in the glass instead of falling back into the bowl. When the glass is lifted fully out of the water, air rushes to the top of the glass and forces the water to fall out.
Try this with a large container of water and larger glass. Do you get the same results? What if you slowly lower the smaller glass into the larger container of water, leaving air trapped inside the glass – does the air pressure try to push the smaller glass to the surface?