Category: Physics

A Raindrop Quiz

12/9/2021

Alexandra Siy
Science through the lens

Which lunch food has a shape that resembles a falling raindrop?

a.      orange

b.     potato chip

c.      hot dog

d.     hamburger bun

e.      all of the above

f.       none of the above

               If you chose (f), you’re like most people who think raindrops are shaped like tears.

               If you chose (e), you’re probably just hungry.

               In either case you’re wrong.

               That leaves us with lunch. Let’s start from the top.

               Choice (a), orange, is a sphere. Water droplets are spherical because water is cohesive, meaning it sticks to itself. The “skin” that holds the drop together is surface tension and the reason insects can walk on water.

               If you chose (a), you made a logical choice based on the properties of water, but you are wrong. Notice that you were not asked to identify the shape of a raindrop sitting on a leaf. You were asked to identify the shape of a falling raindrop. (Always read questions carefully!)

               Moving down the list to (b), we encounter the potato chip. Potato chips come in many shapes, ranging from relatively flat to completely crumpled. Have you ever seen a raindrop that looks even a little bit like a potato chip? If you chose (b) you are wrong, but have a good sense of humor.

               Choice (c), hot dog, is an interesting option. Could a spherical drop of water morph into the cylindrical shape of a hot dog? After all, a hot dog is a cylinder with a hemisphere (half sphere) on each end. Could a water droplet in free fall separate itself into two hemispheres with a long drip of water in between? Although this is an imaginative idea, the laws of physics make it impossible.

               Choice (d), hamburger bun, is the only remaining choice, and is the correct answer. Here’s why:

               A raindrop is acted upon by three forces: gravity, buoyancy, and drag. Gravity is the force that pulls the drop toward the earth, while buoyancy of the surrounding air pushes it upward and keeps it from falling. When the force of gravity is greater than the force of buoyancy, the raindrop falls. The air around it creates drag, slowing the drop down to its maximum speed. In the process, the sphere is distorted into a shape that resembles a hamburger bun.

               Got it? Now, you may go to lunch.

Water forms spherical drops because of cohesion and surface tension. ©Alexandra Siy

Air pressure at the bottom of the falling drop is greater than at the top. (Image courtesy of NASA)

Bugs bite, drink blood, and rob food from gardens and fields. They can even kill plants, animals, and, occasionally, people. Is bugging a crime? In her latest book, Bug Shots, Alexandra Siy compiles "rap sheets" on several of the major categories of bugs and takes a very close look at some of the types of insects in an engaging text. For more information, click here.
Alex Siy is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Siy, Alexandra. "The Race for the Sky." Nonfiction Minute, iNK Think Tank, 7 Dec. 2017, www.nonfictionminute.org/ A-Raindrop-Quiz.

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Isaac Newton's Wonder Years

4/2/2021

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Kerrie Logan Hollihan
Teaching the Power of Wonder

   In spring 1665 a college student named Isaac Newton studied natural philosophy, what we call “science.” Back then, a good student could learn everything to know about the natural world. But plague, the Black Death, came to England. Cambridge University closed. Isaac went home to Woolsthorpe.

            For two years Isaac thought about his studies during four years at university. He’d always been thoughtful—not the best at games, making friends, or minding sheep. But everybody knew Isaac Newton liked to think. Folks told time by the sundial he’d drawn on a wall.

            Home at Woolsthorpe, Isaac’s learning about science and math bubbled up in his head like yeast rising in a loaf of bread.

            So... Newton unplugged. His mind roamed like that of an artist or composer. He was driven by the need to create—not paintings or symphonies, but questions.

            “Why do things always fall down?”

            “Why does the earth move around the sun?

            “Why doesn’t the moon fall onto the earth?”

            “Does everything ‘up there” work like things work ‘down here?’”

            Isaac Newton answered his questions with three science rules, Newton’s Laws of Motion.

            At Woolsthorpe, Newton grappled with the concept of moving objects. He worked out the math to find the area under curves. He called this math fluxions. Today we call this calculus, useful for launching rockets or tracking TV signals.

            Once back at Cambridge, Newton said nothing until he read someone else’s paper on fluxions. Newton published a better paper. Soon he was Cambridge’s top math professor.

            Isaac Newton wondered another twenty years. He played with prisms in a dark room and theorized that white light comprises the visible spectrum of red, orange, yellow, green, blue, indigo, and violet. He practiced alchemy and chemistry, looking for the legendary philosopher’s stone to turn base metals to gold. In 1687, Newton published our most important science book, the Principia.

            In the Principia, Newton showed how laws of gravity and motion work the same at great distances—far off in space, or in your classroom. We accept these ideas, but in 1687 many still had medieval beliefs that sun, moon, planets, and stars all traveled in their own crystal spheres.

            Yes, Newton wondered about A LOT:

Gravity
Forces
Mass
Inertia
Math
Motion
Light
God
???

Whatever interests you, I hope you’ll think about it—a lot! Like Isaac Newton, take time to WONDER!

Sir Isaac Newton was an English mathematician, astronomer, theologian, author and physicist who is widely recognized as one of the most influential scientists of all time and a key figure in the scientific revolution. Based on a portrait by Godfrey Kneller, 1702, via Wikimedia Commons

Sir Isaac Newton's own first edition copy of his Philosophiae Naturalis Principia Mathematica with his handwritten corrections for the twentieth edition. Photograph Andrew Dunn via Wikimedia Commons

Trinity College, the part of the University of Cambridge where Newton worked and lived. Library of Congress

This statue of the young Isaac Newton stands at the Oxford University Museum of Natural History. Look carefully around his feet for a hint on what he is wondering about. If you can’t figure it out, then read about Newton and gravity.
Wikimedia Commons

Featuring 21 hands-on projects that explore the scientific concepts Isaac Newton developed, Kerrie Logan Hollihan's Isaac Newton and Physics for Kids paints a rich portrait of the brilliant and complex man and provides readers with a hands-on understanding of astronomy, physics, and mathematics. A time line, excerpts from Newton's own writings, online resources, and a reading list enhance this unique activity book.

MLA 8 Citation
Hollihan, Kerrie Logan. "Isaac Newton's Wonder Years." Nonfiction Minute, iNK
Think Tank, 21 Feb. 2018, www.nonfictionminute.org/the-nonfiction-minute/
isaac-newtons-wonder years.

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A Bouncing Ball Like You've Never Seen

3/30/2021

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Vicki Cobb
The Master Chef of Kids’ Hands-on Science

You can’t play tennis unless you know where the ball will be after it bounces. You can’t pass a basketball unless you understand how to angle a bounce so that it goes where you want it to go. As long as the court surface is smooth and flat, a ball’s bounce is very predictable. Its path depends on gravity and on the strength and direction of the force that sets the ball in motion. Thanks to high speed photography we can get a closer look at a bouncing ball.

This is a multiple exposure photograph of a bouncing ball. It was taken in complete darkness with the camera shutter open while a high-speed flashing light, called a stroboscope or strobe, flashed 30 times a second. Each flash produced an image.

Here’s what you can learn from this photo: The ball is moving fastest where the images are farthest apart and slowest where they are closest together. When the ball is falling, it speeds up. After it bounces and moves opposite the pull of gravity, it slows down at exactly the same rate as it sped up when it was falling until it stops for an instant and starts falling again. Each time it collides with the ground, some energy is lost. That’s why each bounce loses altitude. If the bounce were perfect, no energy would be lost, every bounce would be as high as the last and the ball would bounce forever.

A strobe also captures the split second when a tennis ball is struck by a racket. The collision flattens the ball, and stretches the strings and distorts the frame of the racket, all in .005 seconds. If these objects kept their distorted shapes, most of the force of the collision would be absorbed. But they are elastic—they restore themselves to their original shapes after they collide. This restoring force is transferred to the ball to change its direction and help add to the speed of the athlete’s swing. The fastest serve leaves a racket at 130 miles an hour. In a rally, a ball-racket collision changes direction of the ball so it is not as fast as a serve, maybe 70 miles per hour. Since the distance between images made by a strobe tells how fast an object is moving, strobes are part of the instruments used to measure the speed of balls from a tennis racket and a baseball pitcher.

Photo credit: C. E. Miller, MIT

In this MIT YouTube, a ball is dropped in front of a meter stick and lit by a strobe light. A long exposure photograph captures the position of the ball at each evenly spaced flash of light. The acceleration of the ball can then be measured from the photo.

Would you believe that you could throw an egg across the room without breaking it? Burn a candle underwater? Vicki Cobb's We Dare You! is a gigantic collection of irresistible, easy-to-perform science experiments, tricks, bets, and games kids can do at home with everyday household objects. Thanks to the principles of gravity, mechanics, fluids, logic, geometry, energy, and perception, kids will find countless hours of fun with the selections included in this book. If you would like to make a We Dare You Video, click here.
Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Cobb, Vicki. "A Bouncing Ball Like You've Never Seen." Nonfiction Minute, iNK
Think Tank, 5 Feb. 2018, www.nonfictionminute.org/the-nonfiction-minute/
a-bouncing-ball-like-you've-never-seen.

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Happy Pi Day!

3/12/2021

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David M. Schwartz

The amazing,engaging, math exponent

Pi Day takes place on March 14th this year, as it has every year since 1988 when this mathematical holiday was invented. Pi Day? Does that sound crazy? Sure it does. It’s irrational. Pi is the world’s most famous “irrational” number. Therefore, Pi Day is the world’s most irrational holiday!

Take a circle, any circle, and divide the circumference by the diameter. The quotient is the number called pi, represented by the Greek letter π. It is a little more than three. How much more? That is a question that people have been working on for centuries.

Pi is an incredibly useful number in mathematics, physics and engineering. It helps us understand things from the shape of an apple to the energy of stars. It helps us design things, from buildings to spaceships.

Pi is an irrational number. That means when you write it as a decimal, its digits do not just end (like 3.5) and they do not repeat in a pattern (like 0.3333…, where the 3s go on forever).

Here is a slice of pi: 3.141592653… The “dot-dot-dot” means the digits keep on going. How far? Is there a pattern?

With supercomputers, mathematicians have probed the mysteries of pi to over a trillion digits. The digits keep going. Infinitely. No pattern has ever been found. (Written in an ordinary font, a trillion digits of pi would go around the world 50 times.)

But the endless, patternless nature of pi enchants many minds and some people delight in memorizing the digits. A 69 year-old man named Akira Haraguchi recited 100,000 digits from memory in Tokyo in 2006. He shattered the previous record of Chao Lu from China, who had memorized merely 67,890 digits of pi after studying for four years.

Can you see a date in the first three digits: 3.14? It’s March 14th — Pi Day! This holiday is celebrated worldwide by students, teachers and math enthusiasts who enjoy pi-themed activities, clothing, jokes and food (namely pie).

This is an ordinary year as far as Pi Day is concerned, but in 2015, Pi Day was really special. After 3.14, the next two digits of pi are 15. So March 14, 2015, was not just any old Pi Day. It was the “Pi Day of the Century.” You’ll have to wait until March 14, 2115, for another Pi Day so sweet!
Happy Pi Day, everybody!

The phrase on this T-shirt would be immediately understood by mathematicians. You won't learn about it for a few more years, but write it down and see if you can find someone who can read it

What better way to celebrate Pi Day than with a pi pie?

This chart shows many ways that pi can be formed -- just so you'll always recognize it when you see it. Pi is a mathematical symbol as well as a letter in the Greek alphabet. Can you find it in the alphabet chart? Hint: it follows Omega.

David Schwartz probes many mathematical mysteries in his books and school presentations given all over the world. He wrote this Nonfiction Minute while celebrating Pi Day at Tashkent International School in Uzbekistan. He is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Schwartz, David M. "Happy Pi Day." Nonfiction Minute, iNK Think Tank, 14 Mar.
2018, www.nonfictionminute.org/the-nonfiction-minute/Happy-Pi-Day.

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Marie Curie: An Elite Player in the Science Game

3/6/2021

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Vicki Cobb
The Master Chef of Kids' Hands-on Science

In October, 1891, 23-year-old Manya Sklowdowska arrived in Paris to attend the Sorbonne, France’s great university. She had saved money, working as a governess to get there. She was determined to make the most of her studies in science and math. Right away she was noticed partly because she was Polish, although she had changed her first name to a French version, Marie, to fit in better. She always sat in the front row of all her classes because her French was not yet fluent and she didn’t want to miss anything. She also was one of only a few female students. In a university full of smart people, she worked hard to excel. She ultimately finished first in her class and went on to make major scientific discoveries.

What made Marie so single-minded and determined? Behind it all was a great love for science, a love she shared with her husband, Pierre Curie, whom she met in 1894. At that time, science was uncovering unimaginable truths in chemistry and physics. New discoveries were being made at a breath-taking pace. Science was like a game and it attracted many players. Why?

1.       There was a Nobel Prize for winners, those who discovered a big idea about the natural world. There was only one nature to discover but people came at it from many directions.

2.       It was collaborative—scientists shared their discoveries by publishing papers.

3.       It was competitive—the papers described procedures so that scientists could check each other’s work. It kept everyone honest. The best work got the most attention.

4.       The discoveries could be applied to solve problems for people. X-rays, light bulbs, phonographs, photographs, movies, and telephones would not have been possible without science.

5.       The biggest prize was the idea of the atom and its structure. Many scientists contributed to modern atomic theory, including Marie.

Marie Curie won the Nobel Prize twice for her work. At a time when women didn't even have the right to vote, she was a working mother of two daughters, a single mother after she was widowed in 1906, the founder of the Radium Institute for research and she brought the x-ray to the battlefield in WWI. She believed that science could save the world, that scientific discoveries belonged to everyone. And she refused to benefit financially from her discoveries. She lived by the highest principles of honesty and integrity. She was a true champion of the science game.

Young Marie Curie (left) with her father and sisters.

Marie and Pierre Curie with their daughter Irene.

Marie Curie's 1903 Nobel Prize portrait

Pierre and Marie Curie in their laboratory.

DK Biography: Marie Curie tells the story of the discoverer of radium, from her childhood in Warsaw, to her experiments with radioactivity in Paris, to her recognition as one of the preeminent scientists of her time.
Filled with archival photographs and amazing fact boxes, this biography paints Marie Curie as the brave and brilliant scientist that she was.

Vicki Cobb is a member of iNK's Authors on Call and is available for classroom programs through Field Trip Zoom, a terrific technology that requires only a computer, wifi, and a webcam. Click here to find out more.

MLA 8 Citation
Cobb, Vicki. "Marie Curie: An Elite Player in the Science Game." Nonfiction
Minute`, iNK Think Tank, 30 Jan. 2018, www.nonfictionminute.org/
the-nonfiction-minute/Marie Curie-An-Elite-Player-in-the-Science-Game.

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A Raindrop Quiz

Isaac Newton's Wonder Years

A Bouncing Ball Like You've Never Seen

Happy Pi Day!

Marie Curie: An Elite Player in the Science Game

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