Tuesday, August 26, 2014

Stomp Rocket

The students brainstormed and played with the parts of the stomp rocket that I made for one of my science projects at The Exploratorium Teacher Institute training program in San Francisco. They had to figure out how to assemble it into the rocket stomp. I asked them an open ended question in the beginning to welcome their creative ideas and new designs from the rocket parts. So, I asked “what can you make out of these parts?’’ It was quite interesting to see the students collaborate their ideas and experiment assembling different models. They came up with different shapes of the alphabet (T, F, h), number (4) and other shapes with their own explanations.
After they tried every possible shapes and designs that they could think of, I asked them to come up with a model of a rocket stomp or a launcher. The students started to rush their ideas into remodeling a rocket stomp. After they figured out their rocket launcher, I gave them some guidance to make the launcher stable.
The next assignment was an art project to make a rocket out of paper or transparent little hard plastic cover or chart paper, cello tape and scissors. I demonstrated how to make a rocket using paper, and asked them to come up with their own designs and shapes for their respective rockets.
The students came up with their creative rockets: some are shorter, others are longer with tails attached and some are without a tail. Everyone was happy with their own rocket and assumed that their rocket would travel to the highest point in the sky. I have also seen students teasing each other with their rockets.
Finally, it was time for all of us to launch our rockets. We all went outside, in front of the guesthouse yard at Chokyi Gyatsho Institute and gathered around a rocket stomp. I told my dear boys that we are going to ‘’estimate’’ the distance travelled by each rocket. The word ‘’estimate’’ was introduced in the class with some daily practical examples (we estimate salt to add in the curries, etc.), before we came outside and they have quite a good understanding of this vocabulary. The students presented the launching of their rockets according to the alphabetical order of their names. Other students in the audience surrounded the rocket stomp, counted down from 3 to 0, while a stomper was ready to give a big stomp on the two liter plastic bottle to push the rocket into the sky.
In the process of launching, the students discovered how a rocket works in general and which of their rockets would travel the longest distance. They knew that a rocket with an attached tail travels further. They also said that a rocket with pointed head, slim, long, straight and airproof ones travel further.
After launching each rocket, I have asked them to estimate the distance travelled by that rocket. They came up with different estimations: 20 feet, 30 feet, 40 feet, 50 feet, etc.
Mr. Sangay Nidup’s rocket travelled the highest distance with an estimated height of more than 50 feet, followed by Mr. Dema Gyempo.









Sunday, August 3, 2014

Feel the temperature

When I was at the Exploratorium in San Francisco, I learned a technique for grouping students for activities in a class by shaking hands and feeling the temperatures. The temperature of human hands varies from individual to individual. Human hands can easily sense the temperatures of other hands.
To investigate we can ask our students to shake hands with other students in the class and notice the temperature of the other hands. Most likely, the students will have hotter or colder than their own hands. 
After shaking hands with many people, arrange them in a line from hottest hands at one end to coldest hands at the other. Then have the hottest handed person and the coldest handed person divide the line into two equal groups- Hot handed group and cold handed group. We can also extend this activity by making the hot handed person and the cold handed person go down the line shaking hands with everyone else to find out the differences.
What’s going on?
Human hands have different temperatures. The temperature depends on the metabolic rate and circulatory system of each individual. If a person’s vascular system is dilated (which is what we call vasodilatation), their hands tend to be hotter, if it is constricted (vasoconstriction), their hands tend to be colder.
We can also try this activity with an adult who smokes and drinks alcohol. First do the above activity then allow the smoker to take a break to smoke . When they return have them shake hand and experience the difference. Nicotine in cigarette smoke is a vasoconstrictor and will cause their hands to become cooler. On the other hand alcohol is a vasodilator and will cause their hand to become warmer. 
In addition to using this information for grouping a class, it can be the entry point to a number of lessons, from anatomy to physics even hygiene. Be sure to wash your hands after touching so many people, hands are the number one way to spread germs.





Tuesday, July 29, 2014

The Pinhole Investigation

The Pinhole Investigation is a very simple activity, but very affective to make students understand and confirm for themselves that the image that comes through a pinhole is reversed from top to bottom and left to right. This activity will provide our students with an opportunity to think and discuss why images appear in reverse, from top to bottom and left to right.
To make a pin hole, we need a sheet of black construction paper, 1 cardboard toilet tissue tube, 1 piece of aluminum foil, 1 piece of wax paper, and 4 rubber bands.
How to make
I will share how I made my pinhole at The Exploratorium Summer Institute Teacher Training Program. I placed the aluminum foil over one end of the toilet tissue tube and secured it with a rubber band. Then I placed the wax paper over the other end of the toilet tissue tube and secured it with a rubber band. Here we were instructed to be careful with the wax paper to keep it as smooth as possible because it is a screen.
Next, I rolled the black construction paper lengthwise around the tube, keeping the aluminum foil end exposed. The wax paper end of the tube became the middle of the black construction paper tube. Later, I came to know that the black tube has its purpose to allow us to see the images more clearly.
Finally, I used a pin to make a hole in the aluminum foil. We were told that sometimes the hole must be enlarged to see the image more distinctly, but it was better to start with a small hole and then make it larger if needed.
What next?
After making a pin hole, each student can take the viewer outside and look at houses, trees, cars, etc. through the open end of the tube. Ask this question to students: What do you notice?
We tried the viewer inside the classroom looking at one red and one green light bulb. We can also try it with a candle.
The following were a few questions we discussed in the class, and we can ask similar questions with the students: Why is the image reversed? How can I make it turn right-side up? How can I make the image clearer? How can I make the image larger? What if I used a larger tube, a longer tube, a larger hole, etc.?





Saturday, July 26, 2014

The Fan Cart

The classic physics problem, the action-reaction pairs in Newton’s Third Law can be explored from one of the projects I have made at The Exploratorium Summer Institute Teacher Training Program.
Let us ask a question to ourselves: “If a sailboat is stuck because there is no wind, is it possible to set up a fan on deck and blow wind into the sail to make the boat move?” The answer to this question can be solved by constructing a “Fan Cart” using simple materials, e.g. a cart, a motor, 4 CDs, a few drinking straws, a fan, a sail, straight round sticks, Velcro fasteners, a pair of small batteries and a battery case.
Make the fan cart look like the one in the pictures or you can design your own. 

Now notice the following observations:
1. Attach the sail and then attach the fan to the cart with Velcro so that it will blow air towards the sail when it is running. Turn on the fan, and observe what happens.
2. Leave the sail in place, but remove the fan assembly and turn it around (or leave the fan assembly in place and reverse the electrical connections to the motor), so that the fan will blow air away from the sail when it is running. Turn on the fan, and observe what happens.
3. Remove the fan assembly, and hold it in your hand while it blows air towards the sail. Observe what happens.
4. Replace the fan assembly so that it will blow air towards the sail when it is running, but then remove the whole sail assembly. Turn on the fan, and observe what happens.
5. Return to the original assembly, with the fan and sail both attached to the cart, and the fan blowing air towards the sail. Now insert a stiff piece of paper between the fan and the sail, and observe what happens.

What's going on?
Here is a summary of the first result from the situations above:
1. Cart doesn't move.
The behavior of the cart is a classic example of Newton's Third Law: For every action, there is an equal and opposite reaction.
In case 1, the fan pushes the air forward, and the air pushes the fan backward. A crucial thing to keep in mind is that the action and reaction forces - often called an action-reaction pair - do not act on the same object. If this was all that was happening, the cart would move backwards; the fan would be pushed backward, and since it's attached to the cart, the cart would be pushed backwards also.


Try to identify the action-reaction pairs in cases 2, 3, 4 and 5 and use them to predict why the cart behaves as it does.

Thursday, July 24, 2014

We can’t believe all that we see

Without a boundary, it's hard to distinguish different shades of gray. Sometimes we can't believe all that we see. Two slightly different shades of the same color may look different if there is a sharp boundary between them. But if the boundary is obscured, the two shades may be indistinguishable.
To try this experiment we can use the image provided below. Attach the white thread tail above the boundary between the two pieces, so that it hangs down and covers the boundary.
The tail like thread is used to obscure the boundary between two gray areas. We see one uniform gray area when the tail is in place, and two different gray areas when the tail is removed. But I have never seen the truth before the experiment. The truth in both gray areas is they are really identical in grades from light gray at one edge to dark gray at the other. In general, our brain ignores slight gradations in gray shades.
If we try this activity with our friends, most of them will see a uniformly gray piece of paper with a rope hanging down the middle.
What is going on?
Actually, the two rectangles are exactly the same. At the right edge both rectangles are light gray. Both become darker toward the left. Where the rectangles meet, the dark part of one rectangle contrasts sharply with the light part of the other, so you see a distinct edge. When the edge is covered, however, the two regions look the same uniform shade of gray.
It is difficult to distinguish between different shades of gray or shades of the same color if there is no sharp edge between them. If there is an edge between the two shades, the difference is obvious.
Your eye-brain system, however, condenses the information it obtains from more than a hundred million light-detecting rods and cones in the retina in order to send the information over a million neurons to your brain. Your eye-brain system enhances the ratio of reflected light at edges. If one region of the retina is stimulated by light, lateral connections turn down the sensitivity of adjacent regions. This is called lateral inhibition. Conversely, if one region is in the dark, the sensitivity of adjacent regions is increased. This means that a dark region next to a light region looks even darker, and vice versa. As a result, your visual system is most sensitive to changes in brightness and color.
When the thread tail is absent and the normal boundary is visible, lateral inhibition enhances the contrast between the two shades of gray. The bright side appears brighter and the dark side darker. When the tail is in place, the boundary between the two different grays is spread apart across the retina so that it no longer falls on adjacent regions. Lateral inhibition then does not help us distinguish between the different shades, and the eye-brain system judges them to be the same.


Wednesday, July 23, 2014

A Simple Oscilloscope

By humming, singing, or talking one can create a variety of cool laser light patterns. This device will allow one to see sound as vibrations or pressure waves. It is called ‘’Vocal Visualizer or Simple Sound Oscilloscope’’ and is one of my first projects at the Exploratorium Summer Institute Teacher Training Program.
I will share how to make this simple device and what is the science behind the working of the device.
We have to cut the pipes into different sizes and arrange it as shown in the picture. Arrange the elbow and “T’’ joints and insert according to the image. Attach the vibration chamber which is made out of drain pipe, balloon and small mirror. Insert the laser into the central single pipe as shown.  Carefully point the laser at the mirror attached to the membrane.
Aim the device on the wall, screen, floor or other reflective surface. Hold the device close to the mouth and hum, sing or just make some weird noises.   
As we make noise, changing the pitch (frequency) and volume (amplitude) we will see a different kind of patterns created on the wall.
What is going on?
When we make sounds, we cause air molecules to vibrate. These vibrating molecules strike one another and hit the rubber membrane. The membrane vibrates, which causes the mirror to wiggle. The laser light bounces off this wiggling mirror, tracing out various shapes and patterns that we can see.
Different amplitude and frequency of sounds coming from your mouth in turn causes different shapes and patterns.
Some shapes look chaotic, others more regular and repeating. Various frequencies will cause the rubber membrane to dance around in resonant vibration modes, in effect creating fluctuating waves. This will be fun for students to learn and play.

Tuesday, July 22, 2014

Colored Shadows: Not all shadows are black

A prism breaks white sunlight up, spreading its component colors out into a spectrum of light visible to the human eye stretching from red through yellow, green and blue to violet. Scientists analyzing these colors find that they have a wave nature, and that one given wavelength of light is perceived as one color when viewed by a person. However, there are colors which do not occur in the spectrum, such as magenta. These colors can only be created when two different wavelengths hit the same spot on the retina at the same time. Without human perception there is no color magenta. Indeed, there is no white either. To understand the colors we must understand the human retina.
The retina of the human eye has three receptors for colored light: one type of receptor is most sensitive to red light, one to green light, and one to blue light. With these three color receptors we are able to perceive more than a million different shades of color.
When a red light, a blue light, and a green light are all shining on the screen, the screen looks white because these three colored lights stimulate all three color receptors on your retinas approximately equally, giving us the sensation of white.
With these three lights you can make shadows of seven different colors: blue, red, green, black, cyan (blue-green), magenta (a mixture of blue and red), and yellow (a mixture of red and green).

White
When red, R, green, G, and blue, B light shine onto the retina in roughly equal amounts, then humans perceive white, W. So we can say that W = R+G+B.

Yellow
When red and green light shine on the screen, humans perceive yellow. So Y = R+G. Now yellow is also a color of the spectrum, which means that yellow is the color humans perceive when the retina is illuminated by a single wavelength of light. The single wavelength for yellow is between the wavelengths for red and green, and the yellow causes both the red and green cones to fire nerve impulses. The electrical signal sent to the brain when the eye is illuminated by one wavelength of yellow is similar to the signal sent to the brain by the combination of two wavelengths R+G.

Cyan
Cyan, C, is a color of the spectrum. The wavelength of cyan light is midway between the wavelengths of blue and green. The crayon that used to be called blue-green is now called cyan, C. Cyan can also be created by adding blue light to green light. C = B+G.
 
Magenta
When we mix blue and red light, our eye perceives the color magenta, M. Magenta is not a color of the spectrum: no single wavelength of light can produce the color sensation called magenta. M = R+B.