Science Smarts: Trouble with the curve

By Patty Rooks on April 5, 2025.

I know it may not seem like it, but I think baseball season is here. Signs have been up all over the city preparing for registration – what an exciting time to take part in some outdoor spring sports!

Unfortunately, I will miss baseball season this year as I do not have any children playing any longer – perhaps I will sneak in a game or two though. When you are sitting in the stands, do you ever wonder about the science behind a curveball?

Well, you know me. Let’s get started!

*Remember to ask an adult before doing this experiment.

Materials

– Sheet of paper

– Scissors

– Ruler

– Pencil

Procedure

1. Using the ruler measure a strip 3 cm x 30 cm.

2. Cut out the strip of paper.

3. Hold the strip of paper to your bottom lip.

4. Blow as hard as you can onto the surface of the paper.

5. Observe what happens.

What is going on?

Blowing on the strip of paper caused the paper to flip up. The force of your breath, or the stream of air coming out of your mouth “pushed” against the bottom of the paper. Because you were holding the paper with it hanging down, the force of your air caused it to rise up.

What is happening here is a scientific principle called Bernoulli’s Principle. Bernoulli’s Principle states that “as air (or any fluid) moves, it creates a region of low pressure. Low pressure has less “pushing force” than air of high pressure”.

When you blew across the upper surface of the strip of paper, you created low pressure. At the same time, air that was beneath the strip kept its normal pressure. The normal pressure is now greater than the reduced pressure at the top, resulting in the strip of paper being pushed up.

Something similar happens when a baseball is thrown.

When a baseball travels through the air, the air flows around the ball. When the pitcher throws a curveball, part of the spin on the ball is in the direction of the flow of air and part of it is in the opposite direction. When the flows of air are in the same direction, it speeds up the ball.

Just as you saw in this experiment, as the speed increases, there is a small decrease in air pressure on that side of the ball and the ball moves in that direction.

At the same time, the higher pressure is also pushing the ball on the other side. This results in a curveball.

Please note, the Praxis office will be temporarily closed as we have to relocate – stay tuned for further details!

Patty Rooks, senior scientific consultant PRAXIS, “Connecting Science To The Community.” Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. Address: 12 826 11th Street SE, Medicine Hat, AB, T1A 1T7 Phone: 403-527-5365, email: praxis@praxismh.ca.

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