Frozen Balloon Illusion

Have you ever seen the illusion where a stream of water appears frozen in mid-air? In this experiment, we’re going to put this cool trick to the test and learn the physics behind it. We’ll see the difference between laminar and turbulent flow, and also learn about the scientists who study it, like meteorologists! 

 MATERIALS:

  • A balloon 

  • Heavy duty tape

  • Bowl 

  • Tray or container 

  • Safety Pin

  • Scissors

TIME ESTIMATED:

10 minutes

DIRECTIONS: 

  1. Use a sink to fill your balloon up with water.

  2. Cut four pieces of tape.

  3. Place the tape on the balloon in the shape of a hashtag. Leave a small square open in the center to poke a hole. 

  4. Put the balloon in a bowl and aim the taped side towards your other container so it catches the water. 

  5. Now use your safety pin to pop the balloon at the center square. Watch what happens to the stream of water! 

THINK LIKE A SCIENTIST!

  1. Why does the water look frozen near the top of the stream?

HOW DOES IT WORK? 

In this experiment, we explored an important area of physics called fluid dynamics. Fluid dynamics is the study of liquids and gasses in motion. When we popped our balloon, the water flowed out very smoothly, which is why it appeared almost frozen. When fluids move like this, we call it laminar flow. The density of the liquid (mass per unit volume), the speed it’s moving at, the length of an opening or obstacle, and the viscosity (the fluid’s thickness) all affect flow. The water flows out of the balloon at a slow speed when it’s near the top of the stream, and the diameter of the hole we created is very small, so the flow is initially steady. Near the end of the stream, the water speeds up due to gravity and the flow gets messy. We call this turbulent flow, and it's one of the most complicated topics in physics! This is because it’s very hard to predict where the water will go next. A surface’s roughness can also make the flow turbulent. Our balloon has very smooth edges, so it didn’t change the water’s course (or velocity) as it traveled out.

FURTHER EXPLORATION: 

Meteorologists are scientists who study the atmosphere, and many use this information to forecast the weather. The atmosphere is a combination of gasses all moving in different ways, so meteorologists use fluid dynamics to study their behavior. When the air is turbulent, the weather can be more extreme and produce stronger winds. Near the lower levels of the atmosphere, the air is especially turbulent because of all the obstacles, like mountains. As we move higher up, the airflow tends to be more laminar, but turbulence does randomly occur. This is one reason why accurate weather predictions can be so challenging!

Anticipated COncerns:

Be careful handling the scissors and safety pin!

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