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Week 29 • 2019/20www.classroomready.com LeVeL 2

WORD POWER

Weekly NewsWater-balloon Physics

It is a favourite activity for children on hot summer days. Take some balloons and fill

them with water, then launch them against an unsuspecting victim, or in a water-balloon battle between friends.

If you have tried this, you will know getting water balloons to work is a bit of an art. Overfill the balloons with water and there is a good chance they will burst in your hands before you have a chance to throw them. Underfill them, or throw them too softly, and they will just bounce off your opponent.

A team of scientists at Princeton University recently studied the physics of water balloons. They studied how balloons change shape and burst on impact against a hard surface.

The scientists’ goal wasn’t to prepare for a big Princeton campus water balloon fight. In fact, understanding the behaviour of liquids wrapped in

a thin elastic membrane (like a balloon) can be quite useful. It can, for example, help engineers and scientists better understand how red blood cells and organs work. Many important parts of the human body rely on thin, expandable fluid-filled chambers to work.

To conduct their experiments, they made elastic capsules about the size of a gumball. They then filled them with water and launched them into a wall using an air cannon. The balloons hit the wall at about 160 kilometres per hour. A camera recorded the wall impacts, shooting video at 20,000 frames per second. Running the camera at this high speed enabled the scientists to study the impacts in extremely fine detail.

In addition to water, the scientists filled the capsules with glycerol and honey. They wanted to see how viscosity affected the impact. The team also used water balloons bought from the store.

The team discovered the balloons behaved like water drops impacting against a surface. This

discovery enabled them to create a simple mathematical model to describe the impacts. This model can be used to figure out the exact values in terms of how full a balloon needs to be, and how quickly a balloon needs to be travelling before it will burst.

This model could be very useful. It can help engineers design fluid-filled capsules to survive impacts, or burst, as needed. And for water-balloon enthusiasts, it might just help them create the perfect water balloon.

In the late 1500s, Galileo discovered a mathematical model that enabled cannons to hit their targets more accurately.

DID YOU KNOW?

Glycerol: A sweet, syrupy fluid. VIscosIty: A measure of how thick and easy the movement of a fluid is. For example, water has low viscosity, while honey has high viscosity.

MatheMatIcal Model: The use of mathematical equations to describe and predict how something behaves.

LEVEL 2 CLASSROOM READY WEEKLY NEWS • WEEK 29 • 2019/20

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Water-balloon Physics1. How is getting water balloons to work a bit of an art?

2. What did a team of scientists study?

3. How is studying water balloons useful?

4. Describe the team’s experiments.

5. What did the team discover? How could they use this information?

CRITICAl THInkInG1. What are your thoughts on scientists studying water balloons?

2. What characteristics are needed to be a good research scientist?

Weekly News Q & a

LEVEL 2 CLASSROOM READY WEEKLY NEWS • WEEK 29 • 2019/20

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the creation of the Water BalloonA water balloon is a latex rubber balloon filled with water used in water balloon fights, during some festivities, and as a practical joke.

The first water balloons appeared in 1950. That was when Edgar Ellington tried to find a solution for a much serious problem - trench foot. Trench foot is a disease caused when the feet are exposed for prolonged periods of time to damp, unsanitary, and cold conditions. He tried to make a waterproof sock by covering a normal cotton sock with latex which would make a sock watertight.

The latex made it difficult to put on a sock, and the socks would rip from being pulled. He decided to try and slowly heat the sock which would make it more elastic. This method made the socks easier to put on, but also made them leak. Disappointed with this, Ellington threw the water-filled sock on the table, and it exploded! Satisfied with this effect, he decided to market a combination of a latex balloon and water to children.

1. What is a water balloon?

2. When did the first water balloons appear?

3. What was Edgar Ellington trying to find a solution for?

4. How did Ellington try to make a waterproof sock?

5. What did he do to make the latex sock more elastic?

LEVEL 2 CLASSROOM READY WEEKLY NEWS • WEEK 29 • 2019/20

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Word PowerUsing the words listed below, fill in the blanks in the following sentences. All of the words have been used in the article.

1. They filled the container with a metallic that was silver in colour.

2. The bag of flour when it fell off of the counter.

3. You should wear a helmet when you are biking to absorb the if you fall and hit your head.

4. That bag is so that you can fit more things inside.

5. Don’t the jug past the fill line or the lid won’t fit.

behaved, bounce, burst, capsules, expandable, fluid, impact, membrane, organs, overfill, unsuspecting, victim

Quiz1. Overfill water balloons, or throw them too softly, and they will just bounce off your opponent.

True False

2. The scientists’ goal was to prepare for a big Princeton campus water balloon fight.

True False

3. A team of scientists at Princeton University recently studied the of water balloons.

4. To conduct their experiments, they made elastic capsules about the size of a .

5. The team discovered the balloons behaved like impacting against a surface.