# Science Experiment: Centripetal Force – Tornado in a Bottle

Science Experiment: Centripetal Force – Tornado in a Bottle

Find More Science Experiments

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.

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.

Print This Post

# Science Experiment: Centripetal Force – Hex Nut Balloon

Science Experiment: Centripetal Force – Hex Nut Balloon

Find More Science Experiments

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:

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.

Print This Post

# Science Experiment: Momentum – Pendulums

Science Experiment: Momentum – Pendulums

Find More Science Experiments

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:

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:

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.

Print This Post

# Science Experiment: Air Pressure – Straw Through an Apple

Science Experiment: Air Pressure – Straw Through an Apple

Find More Science Experiments

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:

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.

Print This Post

# Science Experiment: Heated Gases Expand – Ivory Soap

Science Experiment: Heated Gases Expand – Ivory Soap

Find More Science Experiments

When a substance is heated it’s molecules move faster. You can see this in a pot of water when you heat it on the stove. As the water gets hotter its molecules begin to move until the water is boiling.

When gases are heated, the same thing happens. As gas is heated up the amount of space the gas takes up increases. You can see this by heating up a bar of soap.

You have to use a bar of soap that floats. To make sure you have a bar of soap that will work, float it in a bowl of water. A bar of soap will float because it has air bubble whipped into it. Ivory soap will work for this experiment.

What You Need:
Bar of Soap that Floats
Bowl of Water
Paper Plate
Microwave

Break or cut the bar of soap into four pieces. Put the pieces on a paper plate and microwave for 1 minute. Watch the ivory soap through the microwave window.

As you heat the soap molecules in the air bubbles move quickly away from each other, or expand. This is called Charles’s Law. The same thing happens when you pop popcorn or cook a marshmallow .

Sciece Experiment Idea: Choose different kinds of soap to see what will happen when they are heated up for one minute in the microwave. Be sure to heat each bar of soap up on the same kind of plate and make sure you heat each bar for the same amount of time. The variable in this experiment is the soap, everything else has to be the same. Do the bars of soap each react the same way when they are heated up in the microwave? Why do you think so? Tip: Choose ivory soap for one of your trials – it’s cool!