Science Demonstrations

Bucket Swing

2011-07-01T15:20:00.001-07:00

Swinging Tray

Difficulty: 4 out of 10

Materials:

· Pizza tray

· Plastic cups filled with water

Procedure/ observation:

1. Fill the cups with water and place them evenly on the tray

2. carefully begin to swing the tray in a circular fashion. (Sway it left and right first and then while gaining speed make a full circle) Remarkably, the water is not spilled! As an aside, it is actually quite easy to swing the tray without spilling the water, the difficulty arises when the demonstrator tries to stop swinging the tray.

3. BE VERY CAREFUL WHEN STOPPING THE SPINING

Explanation:

F_c = mv²/r, where F_c = centrifugal force, m = mass, v = speed, and r = radius.

ESIMATE:

cup has mass of 0.35 kg,
radius of the circle is 0.35 meters
rotational speed is 6 meters per second

During this step, the water in the cup is experiencing a force downward due to gravity.
Fg= ma
F_g = 0.35 (kg) * 9.8 (m/s²) = 3.43 (N)

When the demonstrator swings the tray in a circle, there is still a force downward due to gravity. We calculated this force is 3.43 Newton’s. During this step, when the tray is upside down, the cup is no longer being supported by the tray. The water does not fall, however, because it is experiencing an upward force due to its circular motion. The centrifugal force is calculated (see calculation below) to be 6 Newton’s. This force is more than great enough to cancel out the force due to gravity. The fact that the centrifugal force is much greater than the force due to gravity is not surprising. This additional force creates tension on the string which is felt by the demonstrator and allows him to control the swinging motion.

F_c = {0.35 (kg) * {6.0 (m/s)}²}/ 0.35 (m) = 6 (N)

Standing on Light Bulbs

2011-07-01T15:13:00.000-07:00

Standing on a light bulb

Difficulty: 8 out of a possible 10 advise that you explain it and not actually do it if your short on time!

Materials:

· Triangular piece of wood designed with wires and inlets to allow 3 light bulbs to be screwed into the wood (equally apart).

· An electrical cord allows the light bulbs to be plugged in.

· The triangle is an equilateral triangle with sides of length 20 inches.

· 3 light bulbs (NOT fluorescent)

Procedure:

1. The light bulbs are put into the piece of wood which is then turned upside down so that the wood is supported by the light bulbs

2. The wires are connected to the light bulb and then the cord plugged into the outlet

3. Once step two is done the light bulbs should turn on! (this adds a dramatic effect to the demonstration!)

4. A demonstrator carefully places all their weight onto the piece of wood.

5. If done correctly the light bulbs should be able to withstand the weight of the demonstrator.

Explanation:

The catenary shape of the light bulb allows it to withstand the force of gravity and weight that the demonstrator applies on it. Because of the reinforcing nature of this shape, it is very strong and can support much more weight than other round shapes. The exact physics behind the catenary are very complex, but the general idea is that each small portion of the shape is reinforcing the other portions.

Additional information:

Calculating the force applied on the light bulb:

Assume the demonstrators weight is 50 kg
Force of Gravity: 9.8

Fg= Force applied

Fg=ma

Fg= 50 X (9.8)

Fg= 490 N
Therefore the light bulbs are holding 490 Newton’s of force

12 Nails Balance on 1

2011-07-01T15:10:00.000-07:00

Balance Nails

Difficulty: 2 out of a possible 10 very easy!

Materials:

A block of wood with one nail already securely in place
12 identical nails with heads (the nails should be 10 penny size or larger)

Procedure:

1. Putting one nail into the wooden block

2. Place the wood block flat on a desk or table.

3. None of the eleven nails should touch the wood block, the desk or table, or anything else that might help hold them up. No additional equipment other than the wood block and the nails may be used.

4. Put on nail down horizontally, and line four facing toward you on one side and four facing away from you on the other.

5. Put the reminder nail on top

6. Slowly move the now touching nails on top of the one nail which is secured in the wooden block.

Observation/ Explanation:

If the demonstration went right, 10 nails would be balanced on one. The nails seem as though they are defying gravity but in reality their center of gravity is equal to the other side.

Gravity pulls an object down as if all of its weight were concentrated at one point called the "center of gravity." Objects fall over when their center of gravity is not supported. For symmetrical objects like a ball or a meter stick, the center of gravity is exactly in the middle of the object. For objects that are not symmetrical, like a baseball bat, the center of gravity is closer to the heavier end. The stability of the nails depends on their center of gravity being right at or directly below the point where they rest on the bottom nail. Add too many nails to the left or right and they become unstable and fall off. Since the nails have equal weight ratio on all sides the nails do not fall. All in all, due to center of gravity and equal forces acting on the nails causes the nails to appear as though they are defying gravity. (Amazing song my I add)

Laser Show

2011-06-30T14:01:00.000-07:00

Music Laser Show

Difficulty: 5 out of a possible 10, may take some time

Materials:

· Laser

· Mirror

· Speakers (medium or high powered works the best)

· An Ipod or any other source of music connected to your speakers

· A good base song (works the best)

Procedure:

1. Get the speakers ready by pugging them in and connecting them to a music source (ex: Ipod)

2. Attach a mirror to the speaker at an angle that points up. This mirror should be secured directly on top of the speaker, specifically where the music would come out of.

3. Turn on your speaker and play your song on medium to high volume.

4. Make sure there vibration coming from the speaker and moving the mirror.

5. Turn off the lights and point the laser and the mirror.

Observation:

The laser should reflect onto a ceiling or wall. The laser bounces off a mirror attached to a speaker, then goes through a diffraction grating so the patterns will cover an area or a wall or ceiling.

Microwave Soap

2011-06-30T13:58:00.000-07:00

Microwave Soap

Rating of difficulty: 1 out of a possible 10 VERY EASY and simple

Before you start make sure:

Do not leave the microwave unattended during the activity.
Although heating up soap in the microwave will not damage your microwave or the food you heat in it later, it will cause the microwave to smell like soap for a few hours and also your kitchen.
Make sure your remove the packaging and put ONLY the soap in the microwave

Materials:

Bar of Ivory® soap (none other work)
Microwave

Procedure:

Place the soap on the plate (nonmetal) and put it in the microwave.
Set the microwave for 2-3 minutes, turn it on, and watch the soap for the entire time.

Observation:

What you should see is that the soap has turned into a foamy looking substance but still remains a solid.

Explanation:

The soap company adds air bubbles in the soap to save material and make a bigger profit. When the soap is heated instead of melting the air bubbles expand and cause the soap to change into that form.

Additional information:

One can determine how much air is put into the soap but a simple floating test. Just put the soap car into a bucket of water. If it floats it has a high air content if it sinks very low air content.

Electric Rainbow

2011-06-30T13:56:00.000-07:00

Electric Rainbow

Difficulty: 10 out of 10 VERY HARD to perfect. I have personally tried this twice and it did not work. If you are able to make this work PLEASE tell me what you did! Here’s the video for it:

Video : Watch Video HERE

Materials:

· Alligator wire

· 2 paper clips

· Battery

· Water with Sodium Sulphate

· Indicator solution

· Magnet

· dish

Procedure:

1. Put the paper clips on the side of a dish

2. Add the water and sodium sulphate into dish

3. Add indicator solution

4. Connect the wires to the battery and the paper clips

5. Observe what happens

6. Add magnet

7. Observe

Observation:

Hopefully, the sodium sulphate and water mix will change colour once electricity is added into the dish. Also once the magnet is added, one can see the flow of electrons.

Explanation:

Using an electric current and a powerful magnet, we can create a fantastic swirl of colours in a tray of water! This is yet another, unexpectedly colourful demonstration of the connection between electricity and magnetism.

We can break apart water molecules using and electric current. This produces hydrogen gas and oxygen gas. This changes the pH of the water, and we can make those pH changes visible by adding some universal indicator

What happens when we place a small, but powerful magnet into the water? The magnetic field is going to affect the electrical field, and that's going to affect how the colours appear in the water. It looks much better than it sounds, so watch this segment as we create an 'electric rainbow'

Crush Can

2011-06-30T13:50:00.000-07:00

Crush Can

Difficulty: 4 out of a possible 10 easy

Materials:

One metal soda can (EMPTY)
Water in a container bigger than a soda can
Heat resistant gloves or tongs
Heating device (stove or hotplate)
Ice (optional)

Procedure:

1. Put a small amount (about one tablespoon) of water in the empty soda can

2. Heat the soda can on a hotplate (or any other heat source).

3. Fill a large basin with cold water (adding ice would help).

4. Once the water inside the soda can is boiling, grab the hot soda can with tongs , move it over the basin of cold water, and quickly flip it (so that the opening is inside the cold water)

5. The soda can should quickly crumple in on itself.

If it did not work:
Try the experiment again, something went wrong. (Usually either the water in the can was not boiling hard enough, or the can was submerged too much or too little.)

Explanation:

The ideal gas law PV=nRT, where P=pressure, V=volume, n=number of moles (amount of gas molecules/atoms), R is a constant at 8.314, and T is temperature helps us answer this question. Once the soda can was sealed, the volume inside it, and the amount of gas molecules, were held constant. The temperature of the air inside the can dropped because it was originally heated up by boiling water, but then cooled by the ice water. Because the temperature dropped, and everything else was kept constant, the pressure inside of the can also dropped. The pressure OUTSIDE of the can, from normal air, remained constant. Without the inside air pressure pushing back as forcefully, the outside air pressure collapsed the can.

Chocolate chip Microwave wave lenght

2011-06-30T13:47:00.000-07:00

Chocolate chip wave

Difficulty: 2 out of a possible 10 very easy!

Materials:

Chocolate chips
Cardboard
Microwave
ruler

Procedure:

1. Cut the cardboard to fit inside the microwave perfectly

2. Place the chocolate chips all over the cardboard

3. Place in the microwave for 20-30 seconds

4. Take out and measure the distance from the high areas and low areas

Observation:

The chocolate chips should have melted in a wave like pattern showing the wavelength that the microwave produces. This should be around 6 cm.

Explanation:
Chocolate chips are perfect for measuring the distance between melted spots. The heat does not spread as quickly through them because they are not uniform. This means the melted spots will be smaller and you will have more time to measure before they all start to melt.
We now know the frequency of the microwave and can presumably measure the length of the wave, but how are they related to the speed of light? Simple. Electromagnetic waves propagate through free space (like that in a microwave) at the speed of light. Therefore, their length is related directly to the speed of light by λ = c / f where λ is the wavelength, c is the speed of light, and f is the frequency of the microwave. Solving for the speed of light, c = λ * f.

The true speed of light is 2.9987×10⁸.

Balancing Forks

2011-06-30T13:41:00.000-07:00

Balancing Forks

Difficulty: 4 out of a possible 10 easy but may take some practice

Materials:

· Two forks

· One toothpick

· One glass filled with water

Procedure:

1. Start by pushing the forks together (technically referred to as wedging the tines of the forks).

2. Balance the forks on your finger to find the middle point. This is where the toothpick should be inserted between the fingers (tines) of the fork.

3. Carefully rest the toothpick on the rim of the glass. Just slide the toothpick back and forth along the rim until you think you've found the perfect balancing point. Slowly pull your hands away to reveal the amazing balancing fork contraption.

4. You can add another step by lighting the tooth pick on fire.

Observation:

The forks should balance on the glass, this picture is a much better indication of what should happen:

Even after the tooth pick is gone (Because of the fire) the forks should still remain balanced!

Explanation:

Center of gravity: The center of gravity of any object is the point about which you can balance the object as if all the masses were concentrated or gathered at this point. In other words, it's the point at which the object balances from left to right, front and back, and top and bottom. In your balancing fork act, the center of gravity is directly below the spot where the toothpick rests on the rim of the glass. If you look closely at your balancing fork-art, you'll notice that the fork handles are positioned below the toothpick. This actually puts the center of gravity directly below the point where the toothpick is balanced (called the pivot point). Here's where it gets really strange: the center of gravity, where the forks balance front and back, left and right, top and bottom, is actually hanging in mid-air.

Physics Demonstrations!

2011-06-30T13:37:00.000-07:00

Physics Demonstrations

Hello everyone, here is my blog for physics demonstrations! I would like to keep this introduction very simple and say that majority of these demonstrations I have seen done personally. There are very few which I would consider difficult or haven’t seen personally. Along with how to do the demonstration and explaining its results I will give the demonstration a ration out of 10 on how hard it was to execute (1 being very easy and 10 being difficult). These demonstrations come from a variety of places, from classmates, text books and some I have come across from TV shows.

Anyways, hope this blog helps you !