Coanda Effect Worksheet for 11-Year-Olds — Math & Science STEM Activity

Instructions

Welcome! You've built an awesome air ball box. Now it's time to become a scientist and mathematician to figure out the cool physics that makes it work. Grab your air ball box, a light ball (like a ping pong ball), and a protractor if you have one.

Part 1: The Science of Floating

Let's observe the magic of airflow.

1. Place your ball in the stream of air coming from the fan in your box.
2. Watch what happens! In the space below, describe how the ball behaves. Does it fly away? Does it hover? Does it spin?

My Observations:

What's Happening? The Coanda Effect!

You've just seen the Coanda effect in action. This scientific principle says that a stream of moving fluid (like the air from your fan) will tend to "stick" to a nearby curved surface (like your ball). The air flows around the ball, creating a pocket of lower pressure above it. The higher pressure air below the ball then pushes it up, making it float!

Fill in the blanks to test your knowledge:

1. The scientific principle that makes the ball float is called the _______________ effect.
2. The air from the fan is a moving _______________.
3. The air stream "sticks" to the _______________ surface of the ball.
4. This creates an area of _______________ pressure above the ball, allowing it to float.

Part 2: Math & Measurement Challenge

Let's see how stable the ball is. We're going to test how much you can tilt the box before the Coanda effect isn't strong enough to hold the ball.

1. Start with your air ball box flat and the ball floating.
2. Slowly and carefully, begin to tilt the box.
3. Use a protractor to measure the angle of the tilt. What is the maximum angle you can tilt the box before the ball falls out of the airstream?

My Measurement: The box can be tilted about ___________ degrees before the ball falls.

Data Collection: Fan Speed Math

The fan in your box has to spin very fast to create enough airflow. Let's do some math based on a typical small fan.

Problem: If a fan blade spins at 1,500 RPM (Revolutions Per Minute), how many full revolutions does it make in just 10 seconds?

Show your work below. Hint: First, figure out how many revolutions it makes in one second.

Part 3: Think Like an Engineer!

The Coanda effect isn't just for floating balls. It's used in many real-world inventions. The way air flows over the curved wing of an airplane to create lift is a perfect example!

Can you think of and list one other place or machine where controlling airflow over a curved surface might be important?

Answer Key

Part 1: The Science of Floating

• My Observations: Your answer should describe the ball hovering or floating in the air stream. You might have noticed it spins or wobbles but stays trapped in the column of air.
• Fill in the blanks:
  1. The scientific principle that makes the ball float is called the Coanda effect.
  2. The air from the fan is a moving fluid.
  3. The air stream "sticks" to the curved surface of the ball.
  4. This creates an area of lower pressure above the ball, allowing it to float.

Part 2: Math & Measurement Challenge

• My Measurement: Answers will vary depending on your fan and ball, but a typical answer might be between 15 and 30 degrees. The key is that you were able to measure it!
• Data Collection: Fan Speed Math
  • Step 1: Find revolutions per second. There are 60 seconds in a minute.
    1,500 revolutions / 60 seconds = 25 revolutions per second.
  • Step 2: Calculate for 10 seconds.
    25 revolutions/second * 10 seconds = 250 revolutions.
  • Answer: The fan makes 250 revolutions in 10 seconds.

Part 3: Think Like an Engineer!

• Your answer could include many things! Here are some examples:
  • Race cars (using wings and spoilers to create downforce to help them stick to the track)
  • Helicopter blades
  • Drones
  • Sailboats (how the sail catches the wind)
  • Curveballs in baseball