Grandfather Tang's Story

Ann Tompert (Crown Publishers, (New York, 1990)), published a book called Grandfather Tang's Story that uses Tangram 7 pieces as illustrations- you can learn more about Tangram here.
The idea can be very useful in a class room or even at home while playing with our restless.

The story goes like this:

Grandfather Tang

Tangram Grandfather Tang

and Little Soo

Tangram- Little Soo

were sitting under a peach tree in their backyard.

Tangram- Tree

They were amusing each other by making different shapes in their tangram puzzle.

"Let's do a story about the fox fairies, (Chou and Wu Ling)," said Little Soo. So Grandfather Tang arranged his seven tangram pieces into the shape of a fox.

Tangram- Fox

Then Grandfather Tang made another fox with Little Soo's seven tangram pieces. Little Soo clapped her hands as her grandfather began.

Although Chou and Wu Ling were best friends, they were always trying to outdo each other. One day this rivalry almost brought their friendship to a tragic end. They were sitting under their favorite willow tree beside a river talking about their magic powers.

"I can change myself into a rabbit as quick as wink," boasted Wu Ling. "I'll bet you can't do that."

"I can too," said Chou.

"Can not," said Wu Ling. "Anyway, actions speak louder than words." and he changed himself into a rabbit.

Tangram- Rabbit

"Not bad," said Chou, smoothing his whiskers. "But watch me do better than that."

And before Wu Ling could blink, Chou changed from a fox into a dog.

Tangram- Dog

Now, when Chou changed himself into a dog, he not only looked like a dog, but he felt like a dog and acted like a dog. He bared his teeth and lashed his tail. Wu Ling shivered and twitched his nose.

"I love rabbits," Chou growled," and I'm going to get you and gobble you up."

The dog edged closer and closer. Wu Ling's eyes grew bigger and bigger. He was too frightened to move at first. But then he thought, "I'll be safe if I can climb up the willow tree."

His little puff of a tail grew long and bushy and his tall ears shrunk as Wu Ling transformed himself into a squirrel.

Tangram- Squirrel

Wu Ling sprang into the willow tree and scrambled to the top.

"Chou will probably turn himself into a cat so he can climb up the tree after me," Wu Ling said to himself. "But he'll never catch me, I'll jump from tree to tree and he won't be able to follow me."

Of course, Chou thought about changing himself into a cat.

Tangram- Cat

"But that's just what Wu Ling expects me to do," he said to himself. "What can I do to surprise him?" He thought and thought. "I know. I'll swoop down upon him from above" And he turned himself into a hawk.

Tangram- Hawk

Chou circled round and round in the sky above the willow tree, searching for Wu Ling. Wu Ling peered through the leaves of the tree, looking for Chou on the ground. Round and round Chou circled the willow tree until he spied Wu Ling.

"Kek! Kek! Kek!" he shrieked as he zoomed down upon the squirrel.

Wu Ling trembled. Chou's beak looked sharp enough to pierce right through him.

"If only I lived in a shell house," he thought "Then Chou couldn't hurt me."

Chou stuck out his fierce claws to seize Wu Ling, but Wu Ling dove toward the river below the willow tree. And as he dove, he tucked in his head and tail and legs, turned green, and changed into a turtle.

Tangram- Turtle

Wu Ling climbed up on a mossy rock in the middle of the river. He thought he was safe because he looked as if he were a part of the rock. Chou circled round and round, searching and searching, until his sharp eyes spotted the turtle. Then he swooped down, down, down toward him.

But just as Chou reached him, Wu Ling plunged into the water. "Follow me and you'll drown, he cried.

"Don't worry," cried Chou, plunging right behind Wu Ling.

His body grew longer, covered with scales. He whipped the water with his long, wicked tail. And he snapped his spike-toothed jaws as he turned into a crocodile.

Tangram- Corcodile

Wu Ling circled round and round as he plunged down, down, down to the bottom of the river. Chou lashed his wicked tail as he plunged after Wu Ling. Just as they reached the bottom, Chou clamped Wu Ling in his spike-toothed mouth.

"Now, I've got you!" he bellowed through his clenched teeth.

"Oh, no, you haven't," cried Wu Ling, who grew smaller and smaller and changed himself from green to gold as he transformed himself into a goldfish.

Tangram- Goldfish

and he swam out of Chou's mouth between his spiked teeth.

Then he hid in a patch of cattails. Chou churned the water with his lashing tail as he charge into the patch after Wu Ling. With his head swinging back and forth and his eyes darting here and there, he searched for Wu Ling. Wu Ling knew that Chou would not give up until he found him.

"I must fly from here," he thought. And he started to honk as he transformed himself into a goose.

Tangram- Goose

"Honk! Honk! Honk!" called Wu Ling. And he took to the air.

A chorus of honks swelled the air as the flock of geese spread their wings to follow him. While Chou watched, the honking grew fainter, the flock grew smaller, and he felt his anger slowly drain away.

"Why, oh, why did we play that stupid game?" he moaned. "I'll never see Wu Ling again"

He closed his eyes and sank toward the river's bottom. Just as he touched it, however, he had an idea. And up he popped again, a goose himself.

Chou charged after him, but Wu Ling spread his wings and took to the air.

Chou watched him fly to a small island where a flock of geese were feeding. By now he was not only very angry, he was also very hungry. He decided that if he could not catch Wu Ling, any goose would make him a good dinner. He splashed through the water toward the island until he reached it.

Moments later, Chou was flying after Wu Ling and the other geese. He could hardly see or hear them at first. But he did not let this discourage him. Calling upon every last bit of his strength, he forged ahead.

Each flap of his wings brought him closer. The wedge of geese slowly grew bigger. The honking grew louder. At last Chou found himself flying beside Wu Ling.

"I'm tired of our silly game," he cried. "Come back with me to our willow tree."

Before Wu Ling could answer, something stung Chou's right wing. He sank toward the ground.

A hunter had shot him. Wu Ling flew down beside Chou, place his left wing under Chou's smashed right wing, and together they fluttered down to the edge of the forest.

The hunter ran toward them.

"Fly away," Chou urged Wu Ling. "Save yourself. Fly! Fly!"

"I wont' desert you," cried Wu Ling. And with a mighty roar, he changed into a lion.

Tangram- Lion

The hunter raised his bow. Wu Ling sprang toward him and knocked the bow from his hand. The hunter fled, leaving his bow behind.

Wu Ling and Chou returned to their fox shapes. And Wu Ling helped Chou to his den, where he took care of him until he was mended.

"Did they ever play that game again?" asked Little Soo.

"Many times," said her grandfather. "But they were very, very careful,"

"That was a good story," said Little Soo. "Let's do another."

Grandfather arranged his seven tangram pieces.

"Is this story going to be about a man?" asked Little Soo.

"Yes, said her grandfather. "he's old and he's tired. He wants to sit under a tree and rest awhile."

Tangram- Grandfather Tang

"Is he a grandfather like you?" asked Little Soo. "Yes," said her grandfather just like me." Little Soo arranged the seven pieces of her tangram beside her grandfather's.

Tangram- Little Soo

"Is that a little girl?" he asked.

"Yes, said Little Soo. "Just like me. She'll sit and rest beside the man."

"That will make him very happy," said Grandfather Tang. "And now, Little Soo, what will we do?"

"We'll sit and rest together until Mother calls us for supper," said Little Soo.

"That will make me very happy," said her grandfather.

Et Voilá!
Try to make your own stories with the 7 Tans!

Enjoy!

Instant facts- Just add water 31

The bicycle as we know it today – with two wheels of the same size – looks almost exactly the same as one from 1900.
in http://didyouknow.org

Instant facts- Just add water 30

The domain name www.youtube.com was registered on Valentines Day (February 14, 2005)
in http://pcfacts2010.blogspot.com/

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Around 2000 different types of plants are used by humans to make food.
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Looking for the gravity center in a soda can

Another trick from the video. A razão pela qual a lata fica "em pé" é exactamente a mesma da dada no caso dos garfos, é uma questão de centro de gravidade.

What we need:

• 1 soda can,
• water.

How to:

1. Fill 1/3 of the can with water;
2. Place the can on the table with a 40º degrees inclination; 
3. Try to balance it, you will be able to balance the can in a "falling position", if the can starts to rotate over the bottom let it rotate until it stops.

What happens?
There is a position where the can stands in a strange equilibrium.

Why?
Exactly for the same reason the forks found the balance here.
Try this with other recipients and/or cans.

Et voilá!
Magic!

Enjoy!

Looking for the Gravity Center

Yet on this video, the forks trick.

What we need:

• 2 forks alike,
• 1 toothpick or skewer.

How to:

1. Place the forks  like the illusionist in the movie, otherwise you will never make it;
2. Place the  toothpick or skewer between the fork tines, in the middle and up;
3. Place our finger on the toothpick tip, like in the video; 
4. Try to do the same you did on step 3 placing your finger on the opposite side.

NOTE: We didn't have access to a toothpick thick enough to fit perfectly the forks, so we used tape to hold them one to another. This doesn't affect the demonstration.

What happens?
Magic!
In step3 the forks stay on the tip of your finger in a "falling" position.
In the step4 the forks moves in an attempt to find its balance.

Why?
Before anything else we need to understand 2 things:

• Center of mass - this position is defined mathematically. It's the result of an external force acting on the object. This center of mass isn’t necessarily the geometric center of the object.
• Center of gravity, it’s the point which we must apply the force to balance the force of gravity. Imagine a tray, if we want to balance it with just one finger, and assuming the center of mass is at the geometric center, center of gravity is exactly the point where we must apply the force to keep it still but suspended in the air without rotate or fall.

So, what determines the balance of a body is called the location of the center of gravity, in other words the "point of application" of the gravitational force (weight).

Returning to the forks, they are definitely in equilibrium, it's indifferent if we use a finger or any other object (for purposes of this magic trick we will say that our finger has paranormal abilities, but in fact physics takes care of it). Where is the center of gravity? The center of gravity is somewhere between the extremities of the forks.

Some daily examples:

• The equilibrist uses the rod to keep the center of gravity at place, it's important that the center of gravity is above the wire; - The stick helps to restore balance.
• When you grab a large/heavy object automatically you change your body position. This is due to the fact that our body has a fixed center of gravity, when you add more weight/volume to the equation, the body has to readjust the new center of gravity.- Body may assume incorrect positions when transporting heavy loads. 
• Notice that, when a baby is learning to walk, often falls forward or sideways, to us this doesn't make much sense, but the baby is trying to learn where is his balance.- The balance is learned.
• Finally, notice Cristiano Ronaldo, during the games, bends his knees and sudden change his direction, without falling, why? Among other things, because when he bends his knees he makes his center of gravity lower so he can get more balance. The same goes for race cars. A car with a lower chassis is a faster car, why? Because the center of gravity is lower and the car becomes more stable in tight turns and can therefore go faster. - lowering the center of gravity increases the balance.

Try to find other systems in weird balances.

References: efisica.if.usp.br; mundofisico.joinville.udesc.br
Et voila!
Balance in your fingertips!

Enjoy!

Carful with the dishes

From here
At first sight looks easy, but a closer look take us wondering "how did he do that?".
Please do not try this without adult supervision

NOTE:

• The cloth must be small,
• The plates must be placed 1 or 2 in away from the table edge,
• Don't use plastic dishes, they are too light,
• A smooth table will make your task easier.

What we need:

• a table,
• a table cloth,
• plates, cups ad tableware, try just one plate at first.... then add more stuff to the table

How to:

1. Follow the NOTES advices;
2. Grab the table cloth with both hands;
3. Pull it in just in a single fast movement in the floor direction, this step may require training.

What happens?
You pull the table cloth and all the plates remain on the table.

Why?
All the objects on the table are in rest.
All objects in rest need to overcome inertia in order to move.
We already talked about inertia. The Principle of Inertia is the first law of Newton and says:
"All bodies remain in their state of rest or uniform rectilinear motion, unless they are forced to change its state by influence of external forces"
In simple words, the Newton's First Law says: "If something is moving or stopped, will remain in motion or stopped unless something disturbs the system."

Basically what happens is that the objects are at rest on the table, if the table cloth is soft enough, if the board is regular and the pull is fast and clean the dishes will stir but will not fall.  The energy we give to the system table+objects+table cloth it's not enough to make the objects to fall.

Et voilá!
Don't do this at home!

Enjoy!