Tag Archives: Science Experiments

Thick Book Friction

Thick Book Friction

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Every time an object moves on earth it is rubbing against something else; another object, the ground, a tabletop, etc. Whenever two objects rub against each other friction happens because objects are not slick. If you look at objects under a microscope they are actually very bumpy. When the microscopic bumps on objects rub together, friction happens and the object that is moving slows down and eventually stops.

Gravity holds objects on the earth and friction keeps objects from sliding all over the place. Zero gravity looks fun when astronauts get to float but zero gravity makes things hard too. What if everything floated? We would be chasing objects all the time. Now think about what life would be like if there was no friction. You could just slide along the sidewalk with no effort at all…but it would be really hard to steer and stop…kind of like roller blades. The wheels on roller blades help reduce your friction so that you can glide across the ground, but as you know, it is tricky to steer and stop.

Do you know you to shuffle playing cards? You divide the deck in half and then use your thumbs to make the cards alternate as they overlap. If you try to pull the two sides apart, it’s hard – because of friction. All of the cards are rubbing together. However, if you make a bridge, the cards easily fall back into place in one pile. When you make the bridge the cards bend so that less surface area of the cards is touching each other. Less touching=less friction.

 

What You Need:

  • 2 Thick Books

Today’s experiment will show you just how influential friction can be. Phone books works great for this but any two thick books will do. Place the two books on a table. Push them apart – they slide across the table easily. However, if you overlap some of their pages…it’s not NEARLY as easy.

Open two books and overlap each page of the two books. About half of the page of one book is laying on top of about half of the page of the other book – like your are shuffling playing cards.  Now try to pull the two books apart. Can you?

This video will show you just how much strength it takes to pull two phone books apart. Friction is no small force!

Here is a game you can play to figure out how friction affects moving objects:

Here are some websites that will help you understand friction:

Here are some books that will help you understand friction and give you some more friction experiment ideas.

  • Gizmos and Gadgets Chapter “Get a Grip” about Friction (Pages 28-48).
  • Mythbusters Science Fair Book – Is It Possible to Pull Apart Two Phone Books That Are Laid Down With Alternating Pages? (Pages 110-111)
Gizmos and Gadgets Mythbusters Science Fair Book The Science of a Bicycle Friction and Gravity: Snowboarding Science

Words to Know:

Friction -

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Centripetal Force – Tornado in a Bottle

Centripetal Force – Tornado in a Bottle

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A couple weeks ago we learned about centripetal force when we did the Hex Nut Balloon experiment. We learned that centripetal force is what makes an object move in a spiral pattern when it is travelling in a circle, like a penny in a funnel shaped wishing well. Centripetal force is the force that pulls a thing toward the center of rotation….like the little whirlpool that forms when you drain the bathtub or like the Zinga at Holiday World! Why IS that water slide called Zinga? Because in Swahili Zinga means “to move in a circular motion”.

Today, we are going to learn about how liquid and air behave when they are moving in spiral pattern. Have you ever put a coin in one of those wishing wells that is shaped like a giant funnel? The coin rolls around and around the sides of the funnel in smaller and smaller circles until it goes down the hole in the middle of the well? That coin is demonstrating centripetal forceWhat You Need:

  • 2 Liter Soda Bottles
  • Duct Tape
  • Water
  • Food Coloring (Optional)

The tornado in the bottle looks a lot like the water draining out of the bathtub. When liquids pour they make a spiral pattern around a center. This is called a vortex. Gravity is pulling the liquid down toward the hole while the force of the pouring water is rotating around a center point…the middle of the drain or the neck of the liter bottle.

Easy Genius Weather Experiments

Words to Know:

Centripetal Force – A force that makes an object move in a  circular path toward the center around which the object is moving. It is the force that pulls a thing toward the center of rotation.

Vortex – Whirling liquid or gas, like a tornado or the water draining out of a bathtub.

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Centripetal Force – Hex Nut Balloon

Centripetal Force – Hex Nut Balloon

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Have you ever put a coin in one of those wishing wells that is shaped like a giant funnel? The coin rolls around and around the sides of the funnel in smaller and smaller circles until it goes down the hole in the middle of the well? That coin is demonstrating centripetal forceCentripetal force is the force that pulls a thing toward the center of rotation….like the little whirlpool that forms when you drain the bathtub or like the Zinga at Holiday World! Why IS that water slide called Zinga? Because in Swahili Zinga means “to move in a circular motion”. Lots of amusement park rides work because of the laws of physics.

You can use a balloon to demonstrate centripetal force.

What You Need:

  • Balloon
  • Hex Nut

Blow up a large balloon. Before you close the balloon, put a hex nut in it and then tie the end of the balloon closed. Hold the balloon between your hands and move it in a circular motion until the hex nut starts to roll around the inside of the balloon. Now stop moving the balloon and watch what happens to the hex nut. What you are seeing is centripetal force. The hex nut is on a circular path inside the balloon. Things that are moving in a curved or circular motion will slowly move toward the center of the circle, in this case, the bottom of the balloon. What sound does the hex nut make? How about a penny? A marble? Try them all and see how they behave the same or differently.

Here are some websites that will help you look at centripedal force and other physics laws that make amusement park rides work the way they do:

Here are some books that will help you demonstrate Centripedal force and learn more about it:

Naked Eggs and Flying Potatoes Super Simple Things to Do With Balloons Big Roller Coasters Speed and Acceleration

Words to Know:

Centripetal Force – A force that makes an object move in a  circular path toward the center around which the object is moving. It is the force that pulls a thing toward the center of rotation.

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Momentum – Pendulums

Momentum – Pendulums

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A pendulum is a weight hanging from a fixed point. A yo-yo on a string can be a pendulum if you have ahold of the string and hold it in one place while the yo-yo hangs down freely. Pendulums are also associated with clocks or hypnotists, who swing an object back and forth from a fixed point. On a swing, YOU are a pendulum. Pendulums are affected by laws of motion. When a pendulum swings it has momentum. In this video, Bill Nye the Science Guy demonstrates momentum:

srppendulum2

Things You Need:

  • String 3 feet long
  • 2 Strings 2 feet long
  • Two Mugs
  • Two Chairs
  • Scissors

This experiment will show you something surprising about how momentum works. Set two chairs back to back about 3 feet apart. Tie a piece of string to the back of one chair and toe the other end to the back of the other chair. The string should not have a lot of slack in it. Tie a 1 foot long piece of string to the piece of string suspended between the two chairs about 18 inches from one of the chair backs. Now tie the other 1 foot piece of string to the suspended string about 18 inches from the OTHER chair back. When you are done, the two pieces of string should be a about 1 foot apart. Now tie a mug to the end of each dangling piece of string. Pull back on one mug and let go, letting it swing back and forth until it stops. Does it stop? What does the other mug do? When you release the first mug, momentum keeps the mug swinging back and forth. The mug will swing until friction in the air and friction from the string knot rubbing on the handle slows it down.

The weird thing is that when the first mug slows down…the second mug will START swinging, even though you never touched it! Some energy from the first mug travels along the string and makes the OTHER mug start swinging. Even though the momentum of the swinging mugs is slowed down by friction, some of the energy is transferred to the string, which carries it to the second mug.

Science Project Idea: Replace the mugs in this experiment with matching objects of different weight. Try two matching plastic mugs. How much momentum do the plastic mugs have? Does the momentum from a plastic mug have enough energy to pass through the string to the second plastic mug? Try hanging two metal forks from the string. Now try two plastic forks. Which kinds of objects have enough momentum to transfer energy to the second object without even touching it?

Here are some books and websites that will help you explore momentum and understand why heavier objects create more momentum:

Streg Nona: Her Story Many Ways to Move

Words to Know:

Momentum – the product of mass plus velocity. That means the movement that occurs when you consider an object’s mass and how fast it is moving.

Pendulum – A weight hanging from a fixed point.

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Air Pressure – Straw Through an Apple

Air Pressure – Straw Through an Apple

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Even though air seems like nothing, it really is something. Gases like air, even though they are not visible to our eyes, are made up of molecules just like solid objects. These molecules are pulled toward the earth by gravity.

Earth is surrounded by a layer of air that is heavy. That layer of air exerts pressure on the surface of the earth, a lot of pressure. Our bodies are used to it so it doesn’t bother us. In fact, we are so used to it that what bothers us is when the air pressure is gone.

The higher you go in the atmosphere, the less air pressure there is because the “thickness” of the air is less the higher you go. That’s why airplanes have “pressurized” cabins. We can’t survive in too little air pressure.

Today’s experiment will demonstrate just how strong air pressure is.

What You Need:

  • Apple
  • Straw

Take a straw and try to push it into an apple. Hard isn’t it? The straw bends. Now put your thumb over one end of the straw while you try to push the other end into the apple. Now what happens?

When you try to push the straw into the apple the air molecules in the straw are squished closer together. If your thumb is not over the opposite end of the straw the air molecules just spill out the end. However, if your thumb IS over the opposite end of the straw the air molecules are trapped. All those packed together molecules make the straw stay stiff so that it can push into the apple. The straw seems empty, but it isn’t, it is full of air molecules.

Here are some websites and books that will help you undertand air pressure:

That Surprise and Delight Naked Eggs and Flying<br /> Potatoes Wind and Air Pressure

Words to Know:

Air Pressure – The force exerted by the weight of air. Air pressure is the weight of the earth’s atmosphere as it sits on the earth’s surface.

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