Science Smarts: Mysterious forces

By Patty Rooks on September 6, 2025.

I cannot believe summer vacation is over already! Many of us are getting back into a routine of getting up a bit earlier during the week, not to mention the busy weeknight activities many of us have signed up for. With such a hectic start to September, I thought I would keep this week’s activity simple. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Piece of flat, stiff cardboard (thick poster paper should work)

– Glass

– Water

Procedure

1. Fill the glass full of water. Try to fill it as full as possible, without any spilling over the sides.

2. Carefully place the cardboard over the full glass of water.

3. Check to make sure there are no air pockets left between the glass and cardboard.

4. Take your hand and firmly press it down on the cardboard. Hold it there.

5. Take the glass in the other hand and turn it upside down (you may want to do this over a sink or pail).

6. Carefully remove your hand away from the cardboard.

7. Observe what is happening.

What is going on?

In this experiment you are investigating mysterious forces, also known as air pressure. Although you cannot see it, air pressure is all around us. In this experiment, you are probably wondering how the cardboard stays in place if your hand is no longer there. What is helping it stay in place is air pressure. The air pressure outside of the glass is greater than the weight of the water pushing down on the cardboard.

Mark your calendars for the praxis AGM on Wednesday, Sept. 17 at 7 p.m. We are always looking for new board members that want to share their love of science. Contact Praxis for further details.

Patty Rooks, senior scientific consultant Praxis Science Outreach Society. Praxis has moved! We are very fortunate to be located in the Community Futures Entre Corp Building at #202 556 Fourth St. SE, Medicine Hat, Alberta, T1A 0K8. For all your science needs, please email praxis@praxismh.ca.

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