Intro to Physics!

(from ENERGY) Energy is usually invisible. When you are running, can you see the energy coming off your body? No! Can you see a tree using energy to grow taller and stronger? No! Can you see energy inside your refrigerator, keeping your Jell-O cold? No! We can’t see energy, but we can feel it. TRY THIS! Rub your hands together. Now rub them together faster! What happens? What do you feel? The heat that you feel is heat energy.

(from MATTER) Matter can be a solid, liquid, or gas. Do you have ice cubes in your freezer? What happens when you leave an ice cube on your kitchen counter? It melts into a puddle of water! And if you leave that puddle of water on the counter (unless your mom makes you clean it up!), it… DISAPPEARS! TRY THIS! Can you name 15 things that are made of matter—five solids, five liquids, and five gases? Plasma is another state of matter. Have you ever watched a lightening storm from your window? Lightning is a plasma! You know what else is made of plasma? The sun and all of the stars. There’s more plasma in the universe than there are solids, liquids, or gases.

(from FORCES) Magnets can attract or repel each other. Every magnet has a north pole and a south pole. If a north pole and a north pole are put together, they repel each other and move farther away. If a north pole and a south pole are put together, they attract each other and move closer together. TRY THIS! Have fun playing with two magnets! What kinds of things can you pick up with them? Is there anything you can’t pick up with the magnets? What happens when you put the ends of the magnets together? What happens if you switch one of the ends around?

(from WAVES) If you float on your back in a pond, do the waves move you to shore? After a long time they might. But water in a wave isn’t moving across the pond. Water in a wave is moving up and down, up and down. Waves happen because of energy. Energy is an invisible force that travels as a wave. When you see waves in water, it’s the energy that’s moving toward the shore, not the water. TRY THIS! Fill a sink or bucket with water. Float a ball or piece of foam on the water. With your fingers, make some waves in the water! What happens to the ball? Does it travel? Does it move up and down? Does it go anywhere?

GETTING LEVERAGE A lever is simply a bar that tilts on a fulcrum. If you apply effort by pushing or pulling on one part of the lever, the lever swings about the fulcrum to produce a useful action—usually by lifting a load. Seesaw The zookeeper has recently installed a seesaw in the enclosure. Sloth loves it but Sengi isn’t so happy.  Sloth’s effort easily lifts Sengi’s load. Balancing act Sengi doesn’t want to play anymore, so Sloth stacks two tires on one end of the seesaw and gets on the other end. The seesaw balances, but Sloth isn’t having much fun. Sloth and the tires balance, which means they must weigh the same. Roll over, roll over One day, while playing on the seesaw with Sengi, Sloth falls asleep and rolls toward the fulcrum. Sloth’s side suddenly lifts up. Sengi realizes that the farther away something is from the fulcrum, the more it can lift. So, even though Sloth is much heavier than Sengi, as Sloth rolls closer to the fulcrum, Sengi is able to lift him up. This gives Sengi another escape idea! As Sloth rolls toward the fulcrum, he becomes the load. Sengi’s effort can now lift Sloth. Sloth aims to pull the tired down on the far end of the seesaw, to generate more lifting power. Prepare for takeoff! Sloth and Sengi attach a rope to four tired and place them on a branch high above one end of the seesaw. They sit down together on the other side, near the fulcrum. Sloth yanks the rope hard. Splat! When the tires hit the seesaw, Sloth and Sengi are catapulted up into the air with tremendous force, but not quite enough height. Instead of flying over the fence, they crash straight into it. Sengi spent so much time fussing over the force calculations that he forgot to plot their flight path. Can you succeed where Sloth and Sengi failed, by launching them over the fence? 1. Take Sloth and Sengi out of this pocket. Slot together the arms at their bases. 2. Place our heroes on the seesaw, and tap, flick, or slap the other side to send them over the pop-up fence.

GETTING IN GEAR If you add some teeth to a wheel, you make a gear. The teeth allow gears to fit together to transmit force or motion when they turn. Gears are used in almost every kind of machine.  A groundbreaking discovery Sengi sees a book lying in the dirt just outside of the enclosure. One of the workmen must have left it behind. He reaches through the fence, grabs the book, and starts leafing through the pages. Getting inspired As sengi reads, the gears in his brain start to turn and a plan begins to form. What if they could harness the power of gears and construct a machine to tunnel under the wall? Get to work! Sloth is very excited by Sengi’s machine, until he realized that he’s going to have a help him build it. Little and large At last, the machine is built. Sengi runs on the large gear, and the machine jerks into action. The wooden stake rises and falls, strikes the ground, and makes a big dent. Sloth steadies the stake by clinging to it. Another few hits and they will be free! Or so they hope… Trouble ahead? A bad feeling has been nibbling away at Sengi. Something is wrong, but he can’t figure out exactly wat. 1. LARGE SPUR GEAR Sengi turns the large gear by running along its top. The large gear then turns the smaller one. 2. SMALL SPUR GEAR The smaller gear revolves much faster when turned by the larger one 3. CRANK A rod is joined to the small gear by a pivot, forming a crank. This converts the circular motion of the gear into an up-and-down motion. 4. LEVER The rod is connected to one end of a first-class lever by a pivot. 5. FULCRUM This pivot allows the lever to move up and down. 6. STAKE A pointed stake is attached to the other end of the lever. As the gears turn, the stake is driven up and down.

FLOATING Some things float on water while other things sink but this doesn’t depend on how big they are. For example, an iceberg can be huge but will still float on water but a small pebble will sink to the bottom. How can this be? Well, ice is strange — it’s a solid thing that floats on a liquid thing! This means that ice is less dense than water. In liquid water, the molecules can move about next to each other in any old way but when water freezes into ice, it expands and gets bigger. All the water molecules join together in a way that makes them spread out a little bit. Helium is a good gas to blow up a balloon with. It floats because it is less dense than the air. DO WE FLOAT? Our bodies are a very similar density to water, which means we just about float on water. It is easier to float in salty seawater because salt water is denser than fresh water due to salt molecules. A very salty sea, like the Dead Sea in the Middle East, would allow us to float very easily. AYE AYE, CAPTAIN! If huge ships are made of very heavy steel and iron, how does a ship float? Surely, it’s impossible? Ships are not solid metal all the way through or they would sink straight away. The outside of the ship is a steel and iron shell and the inside of the ship is mainly empty space containing lots of air. Air is less dense than water so the ship’s overall density is less than the water which means it can float. Pretty cool, huh, shipmate? UPWARD THRUST Everything in water experienced an upward thrust force. If an object’s weight is smaller than its upthrust, it will float, but if its weight is greater than the upthrust it will sink. The size of the upthrust is equal to the weight of water that the object displaces. So if this ship had a hole and filled up with water, it would gradually become more dense and sink. Quick, abandon ship! DIVE, DIVE, DIVE! Submarines have special tanks that are filled with air or water. When a submarine floats on water, it means that its tanks are full of air. The submarine carefully balances the amount of air and water in its tanks so that it counteracts the upward thrust of the ocean and can dive under water. It is this careful balance of water and air that stops the submarine sinking to the bottom of the ocean.

NEWTON’S LAWS My friend, Isaac Newton, first explained the rules of forces and movement in 1687 by conducting his own experiments. Using what he discovered, he created three famous laws of nature called Newton’s Laws. FIRST LAW An object which isn’t moving won’t start moving unless a force is applied to it. Things that are already moving will keep on moving in the same direction at the same speed until something stops them. THE FORCE OF FRICTION Most things that are moving tend to slow down and stop because they feel the force of friction from whatever they are moving over. If there was no friction, things would keep moving in the same direction at the same speed forever! ON THE SURFACE Different surfaces have different amounts of friction. It is easier to go sledging down a snowy hill in winter than a grassy hill in summer because the snow has less friction than the grass. SLIP AND SLIDE Less friction makes things really slippery, like trying to walk on ice. A large amount of friction makes it really hard to move, like wading through water. Friction can be a hindrance but also a help. If there was no friction when we tried to walk, our feet would just slip back and forth and we’d never get anywhere! SECOND LAW When you push something with lots of mass it doesn’t speed up as much as something with less mass. Thing of pushing a go-cart — if it’s empty, it will be light and easy for you to push. But if it’s got a big bear in it, it will be heavy and much harder to push. ACCELERATING Newton has an equation to back this up: force = mass x acceleration (or F = ma). If one go-cart has twice the mass of the other, and you push them both with the same force, the lighter go-cart will accelerate twice as much as the heavier go-cart. THIRD LAW When one object puts a force on the second object, the second object pushes back with the same force. RECOIL When a cannon shoots a cannonball, it fires it out with a lot of force. But the cannonball also pushes back on the cannon, creating a big spring back called recoil. This is why cannons are made to be much bigger and heavier than the cannonballs, because the more mass a cannon has, the smaller the recoil is.