Fifteen Quick, Attention-Grabbing, Never-Fail, Inexpensive Science ...

[Pages:28]Fifteen Quick, Attention-Grabbing, Never-Fail, Inexpensive Science Demonstrations!

Always practice the demonstrations before presenting them to a live audience so that they truly are "Never Fail!"

Written and Compiled by: Barbara J. Shaw Ph.D.

Colorado State University Extension 4-H programs are available to all without discrimination.

1

Physics

(5 demonstrations)

Three Laws of Motion ? First Law ? Inertia Demonstration #1: The Table Cloth

What you need (one set): Table (smooth edge) Tablecloth Heavy metal silverware Heavy plate (stoneware is perfect) Heavy drinking glass (glass)

Broom and dustpan (just in case) Plastic ware Plastic plate Plastic cup

Introduction: The First Law of Motion ? Inertia ? An object at rest remains at rest, and an object in motion continues in a straight line, at a constant speed, until a force acts upon it. This law is much easier to demonstrate using "an object at rests remains at rest until a force acts upon it." If you do any demonstrations in microgravity (like on the International Space Station) then by all means, demonstrate "an object in motion continues in a straight line, at a constant speed, until a force acts upon it!" The forces on Earth (gravity and friction from the air molecules) immediately act on any object in motion.

Directions: Put the tablecloth over the table. Set the table with the plastic ware, plastic plate, and plastic cup. With a flair and flourish, grab the edge of the tablecloth, and face your audience. Ask what will happen when you jerk the tablecloth. Wait for responses. Ask for a drum roll. Jerk the tablecloth. The plastic ware, plastic plate, and plastic cup will fly everywhere. Act embarrassed. Put the tablecloth back over the table. Reset the table, but this time use the metal silverware, stoneware plate and glass cup (showing the audience that it is indeed breakable) Ask for a victim ? oops, I mean volunteer. Whisper to your volunteer that when they jerk the tablecloth, they need to jerk fast and down towards the floor. If they jerk up, it will flip the table setting. Ask the audience what will happen now. Direct your volunteer to jerk the tablecloth. Ta Da! Discuss the results.

Explanation: The first law of motion, Inertia, tells us that an object will stay at rest until a force acts upon it. The objects are the place setting items. In the first part, everything goes flying, because the forces of friction (tablecloth rubbing against the place setting) acts much more quickly because the mass of those items is very low. When you use the heavier

2

place setting, it takes longer for the forces of friction (tablecloth rubbing against the place setting) to act on them. The difference between the two place settings is because of momentum. Momentum is a property of a moving object by that determines the length of time required to bring it to rest or start it moving when under the action of a constant force. It takes longer for a semi-truck to accelerate to 35 mph than you in your car. Your car is much lighter (relatively speaking) than the semi. Same holds true for stopping. You can stop in a much short distance that it will take the semi.

Three Laws of Motion ? Second Law ? F=ma Demonstration #2: The Turkey Baster Bulb

What you need (1 for every team of partners): baster bulbs ping pong balls

heavier balls the same size as ping pong balls

Introduction: The Second Law of Motion ? F=ma ? This law is described by a mathematical equation, although everyone completely understands it.

F = force (something that pushes or pulls on an object)

m=mass (weight is the mass pulled down by gravity; weight can change depending on the planet, but the mass remains the same)

a=acceleration (the increase or decrease rate of travel of an object; note that a negative number indicates that the object is slowing down)

The harder you push a toy car, the farther it will go. If you don't push it as hard, it won't go as far.

Directions:

With flourish and flair, place the ping pong ball into the top of the baster bulb. Ask the audience what will happen if you barely squeeze the bulb. Wait for responses.

Barely squeeze the bulb. With flourish and flair, place the ping pong ball into the top of the baster bulb. Ask the audience what will happen if you squeeze the bulb with all your might. Wait for

responses.

Pretend that you are going to squeeze the bulb but don't. Instead, stop and look at the audience.

Ask them if they would like to try this out for themselves. Ask everyone to wait until everyone has the supplies.

NOTE OF CAUTION: If you try to push the ping pong ball into the baster too far, it will get stuck inside. Direct the audience members to just make a seal, and not push too hard.

Distribute the bulbs and ping pong balls. If your participants are working as partners, direct them to alternate squeezing and retrieving the ping pong ball. Allow ~5 minutes.

Get everyone's attention. Ask what will happen if they use a heavier ball than the ping pong ball. Wait for responses.

Exchange the ping pong balls for the heavier balls. Allow ~5 minutes. Discuss the results.

3

Explanation:

It is really intuitive. I have a turkey baster bulb, and I put a ping pong ball in the

opening. What will happen if I barely squeeze the bulb? The ping pong ball was barely

pop out of the baster. If, instead, I squeeze the bulb as hard as I can, then that bulb will

go flying out. Now, instead of a ping pong ball, I use a bowling ball (assuming that I can

find one the same size as the ping pong ball). Squeezing as hard as I can, which ball will

go farther? The ping pong ball! This equation tells us why (using pretend numbers):

F (force) = 12

F = m x a

m (mass) = 2 (light object)

12 = 2 x ?

a (acceleration) = ?

Acceleration = 6

How about this?

F (force) = 12 m (mass) = 4 (heavier object) a (acceleration) = ?

F = m x a 12 = 4 x ? Acceleration = 3

You can see from the numbers above, that a lighter object will accelerate more (and thus go farther) than the heavier object. The force remains the same. You can plug in real numbers to figure out the force applied, or if you know the force, you can figure out either how far will the object travel, if you know the mass, or determine the mass if you measure how far it travels. I love math!

Three Laws of Motion ? Third Law Demonstration #3: Balloon Cars

What you need (1 for every team of partners): Balloons Bendy straws

Scotch tape Large toy cars

Introduction: The Third Law of Motion ? Action/Reaction ? For every action, there is an opposite, but equal, reaction. The meaning of the third law is easier to understand if you replace the words "action" and "reaction" with the word "force." Remember, a force is something that will push or pull an object.

Directions:

Set out the supplies. Tape the straw to the car with the long end pointed towards the rear of the car, and the short end by the front of the car.

Blow up the balloon and twist the neck so that the air won't escape. Ask the audience what will happen if you attach the balloon to the straw and let it go.

Stop. Ask the audience if they would like to do this for themselves.

Ask them if they would like to try this out for themselves. Ask everyone to wait until everyone has the supplies.

4

 Distribute the cars, straws, balloons, and tape. If your participants are working as partners, direct them to alternate squeezing and retrieving the ping pong ball. Allow ~10 minutes.

Discuss the results.

Troubleshooting: Be sure that the straw is taped correctly, with the long end pointed midway between the rear wheels of the car. Be sure that the balloon neck is twisted so that they participants can get it sealed around the balloon before releasing the air.

Explanation: Rockets leave Earth's gravity because of the third law of motion. The action is the expanding oxygen and hydrogen gases as they are ignited, and the reaction is the rocket is propelled towards the sky. In our experiment, the action is the participant blowing air into the balloon, and the reaction is the car propelled by the thrust of the air leaving the balloon. If the participant blows up the balloon until it is about ready to burst, the car will go a lot farther (assuming that the straw has been correctly taped in the correct direction. If the participant barely blows up the balloon, the car won't go very far.

Light Demonstration #4: Colors in White Light

What you need (1 for every participant): Flashlight Red, green, and blue gels Masking tape

White wall or screen in darken room Prism Scissors

Introduction: Primary Colors of Light ? What are primary and secondary colors? What are the colors in a rainbow?

Before the demonstration: Set aside one flashlight for the prism. Cut out red, green, and blue gels using the diameter of the flashlight's plastic window. The gels should be equally distributed among all the flashlights. For example, if you have 16 flashlights, 5 will get red gels, 5 will get green gels, 5 will get blue gels, and one has no gel. Dismantle the flashlights, and place one gel inside the plastic window, and reassemble. Repeat until all but one flashlight have the gels.

Directions:

On the white wall or screen, put a small piece of masking tape. Turn out the lights. Ask the participants what happens when you shine a light though a prism. Wait for

responses.

Shine your flashlight though the prism. You will need to turn the prism until you see the rainbow colors. Focus the rainbow until tight and bright.

Ask participants what makes the colors. Wait for responses.

5

 Ask students to leave the flashlights switched off until you give them directions. Distribute 1 flashlight per participant. Announce to the group the color of the flashlight.

Point to the piece of masking tape (you may need to shine your flashlight on it). Remind the participants to keep the flashlights switched off.

When you give them permission, you would like them to shine their flashlight, aiming it directly on that piece of masking tape.

Before you give permission, tell the participants to observe the colors that they see.

Give permission to turn the flashlights on. You will need to refocus the group to aim their light directly on the piece of masking tape. When they finally achieve that fleeting success, ask what color of light is on the very center of the masking tape (white light).

Standing next to the light, hold your hand up, and about 6" away from the masking tape, so that your hand will cast shadows.

Wait for the oohs and aahs!

Allow participants a minute to make the room dance with the three colors of light, and then direct them to turn off the flashlights.

Discuss the results.

Explanation: Visible light appears white, but actually is made from the rainbow of colors (ROY G. BIV ? Red, Orange, Yellow, Green, Blue, Indigo, and Violet). When they are all mixed together, the light appears white. As light travels though a solid, transparent object, like the prism, the different colors travel differently, and we can see them separated on the other side of the prism (or raindrop).

The primary colors of pigments, or anything that is made from atoms, are red, yellow, and blue, and the secondary colors are orange, green, and purple. Most children know that to make purple, they need to mix red and blue. To make orange, they mix red and yellow, and to make green, they mix yellow and blue. Light is different. It is not made from atoms, but it is a form of energy. The primary colors of light are red, green and blue, and the secondary colors are magenta, yellow, and cyan.

With the prism, we are able to separate each color of light, and with the flashlights, we put the primary colors together, and we see white light. Sir Isaac Newton was the first person to determine that the colors we see are not inside the prism, but made up of the light itself.

Sound Demonstration #5: Groan, Squawk, Gong, and Whir!

What you need (1 set made ahead):

Bullroarer (directions below) o Thin ruler with hole in one end o String o Rubber bands o Plastic spoons

Quacking Duck (directions below) o Heavy duty plastic cup o Nail o String o Sponge o Water

6

What you need (1 for every participant): Heavy duty plastic cup String about 18" long Large paperclip Large nail

Large balloon Hex nut

Introduction: Sound is produced by compression waves (waves that travel like an accordion). Those waves strike your eardrum, and that membrane starts to vibrate. Those vibrations cause an inner membrane to vibrate in a chamber filled with liquid, your inner ear. Those vibrations are translated into the liquid. Tiny "hairs" in that inner chamber move from the vibrations translated in the liquid, and your brain interprets that as sound. You can use two of these experiments as demonstrations or to get attention from your audience. The other two are quick activities for your participants to make and take.

Before the demonstration: To make the Bullroarer, tie the string (about 3 feet long) through the hole of the ruler. Stretch the rubber band lengthwise over the ruler. To operate, twirl in front of you or over your head (like a lasso). If it isn't very loud, twirl in the other direction. Change speed. Optionally, you can make different sizes, including one as small as a plastic spoon. Tie the string by the bowl of the spoon. Stretch a rubber band lengthwise over the spoon. Twirl in front of you or over your head. Is the sound the same? Higher or lower? Louder or softer?

To make the Quacking Duck, carefully punch a hole in the cup with a nail. Thread a string (about 2 feet long) through the cup. Tie one end of the string to a large paperclip. This needs to be on the outside of the bottom of the cup. The string should be hanging out of the cup. On the other end, moisten and tie a sponge (about 1"x2" piece works perfectly). With a moist sponge, pinch the string inside the bell of the cup and pull down the length of the string. As the string becomes wetter, the sound gets louder.

Directions:

Twirl the Bullroarer for attention.

Quack the Quacking Duck.

Ask, what is common about these two sounds? Wait for replies. (Both are made from vibrating air.)

Beautiful Chimes ? distribute plastic cups, string, paperclips and nails.

Direct participants to up the cup with the bottom up. With the nail, carefully put a hole in the center of the bottom of the cup.

Thread the string through the hole. On the outside of the bottom of the cup, tie the nail. On the inside of the bottom of the cup, tie the paperclip.

Pull the string on the nail side, until all of the string is coming out of the bottom on the outside of the cup.

Direct participants to place their ear over the open end of the cup, and gently swing the nail into a chair or table, listening to the sound.

Wow!

7

AND/OR Twirl the Bullroarer for attention. Quack the Quacking Duck. Ask, what is common about these two sounds? Wait for replies. (Both are made from vibrating air.) Whirring Balloon ? distribute balloon and hex nut. Instruct the participants to squeeze the hex nut through the neck of the balloon. Blow up the balloon about half full (WARNING ? ONLY HALF FULL). Tie off the neck of the balloon. Holding the balloon in one hand at the neck, palm down and fingers and thumb extending onto the balloon, start to make circular motions to move the hex nut in a circle on the inside of the balloon. WOW! Discuss the results.

Explanation: All sound is caused by vibrations. There are all kinds of different sounds because different materials vibrate differently.

For the Bullroarer, the air passes through the holes at a faster speed than the air that is going around the ruler or plastic spoon. This causes the whirring, rushing air sound.

The cup on the Quacking Duck amplifies the sound, which is caused by the vibrating string.

The beautiful chime sound you hear from clanging the nail while listening in the cup is because the sound is traveling through solid (the string) rather than in the air. When you clank the nail without holding the cup to your ear, the dull clank is only traveling through the air. The difference in sound shows how much of the sound is lost in the air. Solids and liquids are much better at carrying sound waves.

A hex nut has 6 sides, and these flat edges causing the hex nut to bounce inside the balloon. The whirring sound is made by the sides of the hex nut vibrating against the inside wall of the balloon.

8

 ................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download