Chanukah science...spinning tops

What do bicycles, frisbees, yo-yos, hula hoops, dreidels, and even the earth have in common? They all spin, and so long as they spin the better they are at resisting what gravity is trying so hard to get them to do, which is tumble and fall.

This week we talked about how dreidels work and then we observed the optical illusions produced by spinning tops with different colorful patterns. We finished up by making our own tops using old CDs.

Catapults

This week the kids were challenged to reverse engineer a catapult. Presented with some old broken catapults, the kids had to figure out how they were made. Then, using slightly different materials, they modified and improved this initial design to produce catapults of their own. These catapults are examples of a 3rd class lever .

Seesaws

This week we started talking about simple machines. The first machine we looked at was the lever. After discussing the 3 classes of levers and examples of each, we experimented with a class 1 lever, the seesaw. Each lab group was given a pair of unequal weights. The goal was to figure out how to place them on the seesaw, so that they would be perfectly balanced. In each case we recorded the distance from the fulcrum. After trying out several different pairs, we reviewed our data and looked for patterns.

Let's see how much YOU know about levers...If you place a 500 g weight 10 cm from the fulcrum, where do you need to place a 100 g weight so that it will balance the heavier weight?

Catch me, I'm falling!

Why do some objects fall faster than others?

We reenacted Galileo's experiments in Pisa to test whether an object's weight influences its speed. After a quick trip up the Leaning Tower of Raanana (aka my stairs) like Galileo, we concluded that weight DOESN'T matter, and that how fast an objects falls is the result of an object's air resistance, i.e. the friction between the object and the air as it moves.

From there we naturally moved on to the subject of parachutes, objects specifically designed to maximize air resistance to keep jumpers from hitting the ground too fast. We dropped balls of modeling clay with and without home-made parachutes and compared flight times and the effects of hitting the ground on our jumpers.

See this TED ED talk for a great way to think about gravity

As an extra bonus this week, we also caught the solar eclipse. Thanks to my husband, Danny for the heads up about the eclipse and for showing us how to safely project the image of the sun on to a white board using binoculars. Of course, you should NEVER look through a telescope or binoculars to point them at the sun. Doing so can result in partial or total blindness.

Slip sliding away

The kids took what they had learned previously about friction to the field. We spent the first half of the lesson planning out a controlled experiment to compare the "slidability" of different materials. Then we walked to Park Mapu, where the kids worked in groups measuring the time it takes to go down the slide on a range of materials including: a towel, a piece of card board, and a fleece blanket.

Slippery Slope

Which surface has the most friction with a coin?
To figure this out, we placed a coin on top of different materials, gradually raised one end of the material until the coin began to slide, and measured the angle using a protractor. The idea being, the steeper the angle necessary to get the coin moving, the greater the friction between the material and the coin. 

Next week we hope to apply our results to the larger question: What can you do to reduce the friction on playground slides? Let's hope for good weather!

The Tortoise, The Hare, and You!

Usain Bolt is unquestionably the fastest human alive, but how would he do if he had to compete against other species, like say a grizzly bear? In 2009 he broke the world record, running 100 meters in 9.58 seconds. That's faster than 10 m/s and around 38 km/h. This week we looked at some data on the maximum speeds of different animals and then tested our own local humans.

Most of us fell somewhere between a chicken and a pig.

Go Speedracer Go!

It's just amazing what you can learn using the Encyclopedia Britannica. In fact if you stack 4 or 5 of them, you can build a pretty cool ramp, great for exploring the concepts of motion. Get a couple of toy cars and you're ready to roll! Measure the length of the track, how long it takes each car to reach the bottom, and you've got everything you need to calculate their speed.

Physics: Quiz boards Day 2

This week the kids finished their quizboards - hopefully by now you've seen them, played with them, and hopefully not broken them! This was NOT an easy project. It took a lot of patience and attention to detail, checking and rechecking connections in the circuits, but in the end it paid off. "Operation's" got nothing on these quizboards.

Physics: Quiz board

This week the kids started to build quizboards.

What's a quizboard? A quizboard is a game in which you try to match up questions with the correct answers. If you succeed, a light bulb turns on, and if you get the question wrong, nothing happens.

Interesting child psychology fact: When I do this activity, it is ALWAYS the case that kids suggest adding features to the quizboard that will punish players with a beep or even a shock for wrong answers. Go figure...

As of last week the kids have written their quizzes and started building and insulating the wires that will connect questions and their respective answers. Next time we meet they will complete their quizboards and bring them home.

Physics: Circuits are cool!

This week's experiment was originally called: "Experimenting with different kinds of circuits," but about 5 minutes into it, the kids decided to change the name to "Circuits are cool." We did, and they are. The kids learned about the parts of a circuit: battery, load, and wires, and they were challenged to build circuits that could turn on light, motors, and annoying beeping machines. What's that saying...necessity is the mother of invention? Following their success with the annoying beeping machines, we introduced the concept of switches. Ah....sweet silence.

Physics: Static Electricity

Believe it or not?!

• A balloon sticks to the wall.
• A stream of water bends.
• Two strips of plastic torn from a bag held side by side sway in opposite directions from each other.

Like most magic tricks, what you see is never the whole story. What causes materials to be attracted to or repelled from other materials is a phenomenon called static electricity, an imbalance in charges. This week we tried to understand a little more about how electricity works at the atomic level. To do so we reviewed the atom's basic structure, including positively charged protons, neutral neutrons, and most important for our topic, negatively charged electrons. We talked about how atoms that gain or lose or electrons becomes charged, and are then attracted to oppositely charged materials.

Physics: Batteries

This week we introduced a new topic: electricity. We started off by examining some batteries, taking note of things like voltage and the fact that every battery has a positive and a negative terminal. After a brief discussion about what batteries are and how they work, the kids made batteries out of grapefruit and strips of copper and zinc. Using a voltmeter we confirmed that our batteries worked. A single grapefruit has a voltage of around 1 v, which compared to your 1.5 v AAs is no small potatoes (FYI potatoes make great batteries too)! We attached wires to the battery, hooked up an LED, and NOTHING. Apparently 1 v is not enough voltage to power an LED. But, when life gives you lemons,make lemonade, or in my case, when life gives you a grapefruit tree, make several grapefruit batteries in series and voilà! Let there be light!

Physics: Sound waves

This week we continued exploring sound. We used slinkies to model how sound waves work and then spent some time experimenting in this really cool online sound lab.

Physics: E.T. phone home

While we're on the topic of sound I thought it would be a great time to learn how to make cup-phones. Problem is I had never really done it before. I knew we'd need cups and string, but what kind of cups? Thick string or thing string? Does the material matter? Tough questions, but lucky for me, like Thomas Edison, I've got a stable of engineers in my very own Menlo Park. Given a range of cups and strings to choose from, the kids tested out different models. By the end of the hour I expected a full report on how to make the best cup phone and time-permitting, the pros and cons of various cell-phone plans.

Physics: Good Vibrations

This week we started a new topic: SOUND. We talked about what a sound is and experimented with sounds produced by different materials. The kids made oboe-like straws, plucked rubber bands of different widths and lengths across shoe boxes, bounced wooden sticks off the side of tables, and struck water-filled glass jars, noting in each case how different changes affected the pitch. Finally, the kids used their observations to created their own instruments, and then we had a concert!

Physics: Pulleys

Our goal this week was to raise a 300 g weight a distance of 30 cm. To do this we used a new kind of simple machine, the pulley. We built 3 different kinds, and in each one analyzed the user's experience.
All pulleys PULL, but up or down? How much string do you need to use? and most importantly...Does it feel any easier than just lifting the weight on your own?

Physics: You spin me round round baby round round

What do bicycles, frisbees, yo-yos, hula hoops, dreidels, and even the earth have in common? They all spin, and so long as they spin the better they are at resisting what gravity is trying so hard to get them to do, which is tumble and fall. This week in physics, we played dreidel with a twist. Instead of playing dreidel for gelt, we played dreidel WITH gelt. The kids prepared 3 dreidels as follows: Each one had a plate with 4 coins attached either at the center or at the periphery in one of two possible patterns. The goal was to see which distribution of weight allowed the dreidel to spin the longest. Here's your clue: How is the weight distributed on a bicycle wheel? Is more of it at the center or along the periphery?

Physics: Newspaper Skyscraper

Every building enterprise requires the architect to overcome the forces of gravity and wind to literally rise to the challenge of building something both tall and stable. In our case, the kids were challenged to build skyscrapers out of newspaper and tape. Through trial and error the kids figured out different effective building techniques (e.g. folding the paper into various shapes and building a wider/heavier base).

Afterward we evaluated each tower by measuring its weight, height, and stability in the face of a powerful blow dryer. One of the interesting things we noticed was that different designs privilege one characteristic at the expense of another, meaning it's really hard to build a tower that is both stable and tall.

Physics: What color is it really?

This week we did 3 mini-experiments to investigate how we perceive color. The first was with spinning color wheels. The kids compared the patterns of the discs when still to the patterns they saw when the discs were spun. The second mini-experiment involved looking at magazine pictures under the microscope and comparing the images seen with the naked eye to the colors seen at greater magnification. The third was simply giving each kid some red, blue, and yellow paint and letting them go wild...well on paper anyway.

When we physically combine red, blue, and yellow paints in different proportions we can create an enormous range of colors. Similarly the human brain will combine colors that your eyes see when those 2 colors are seen in rapid succession, as in the case of the spinning color wheels or when they are placed very close together, as revealed by a microscopic examination of pictures from a magazine. What is especially cool about the magazine pictures is that no matter what color you "see," when examined under the microscope you realize that the image is made up of just 3 colors: magenta, cyan, and yellow (aka red, blue, and yellow). By producing images that include different ratios of the primary colors, you can get just about any color.