Wednesday, January 26, 2011

Physics: Two eyes are better than one

This week we investigated depth perception, the ability to perceive the world in 3 dimensions. We carried out a few tasks that require depth perception, and compared a subject's ability to do them with one eye vs. two eyes. For the most part, we found that depth perception requires the use of two overlapping fields of vision, i.e. two eyes as opposed to one, with the two eyes being located along side each other. After discussing our results, we talked about some of the challenges involved in comparing the use of one eye vs. two eyes. Next week the kids will design an experiment to test whether one uses depth perception in a game of catch. Hopefully the kids can use some of their critiques from this week to help them design a fairer and more controlled experiment next week.

Biology: Sensational Skin

This week we investigated a type of cell called the sensory receptor. These receptors are found in our skin and allow us to feel pressure, pain, heat, and cold. The kids made pressure probes (see photo), which were used to test 4 different areas of the body: fingertip, forearm, cheek, and calf. The idea was to GENTLY poke these areas with the probe, gradually decreasing the distance between the 2 toothpicks until the subject could only feel 1 prick. The area with the smallest 2-point discrimination was the area that was most sensitive and was assumed to contain the highest number of sensory receptors for pressure. The kids were surprised to find quite a great deal of variation. Subjects could distinguish 2 distinct pricks at an average of 2.5 mm on their fingertips, while the 2-point discrimination was much larger for the calf and forearm - as much as 7 mm.

We concluded by discussing why it might be adaptive for some areas to be more sensitive than others.

General Science: Let your fingers do the talking

This week the kids learned about fingerprints, you know...dactyloscopy. They used graphite from their pencils and transparent tape to record each of their fingerprints. Then we looked at some common patterns and used these to classify them. Finally the kids produced a single "mystery" print which their partners were challenged to identify using the database of labeled fingerprints.

Sunday, January 16, 2011

Physics and Biology: Newspaper Skyscraper

This week the kids were challenged to build a skyscraper out of newspaper and tape. The question was: how do you use such a flimsy material to build something that is both tall and able to withstand powerful winds. Through trial and error the kids learned that they could increase the strength of the newspaper by rolling or folding it in different ways as well as that building a wider/heavier base makes the tower more stable.

Afterward the kids evaluated each tower by measuring its weight, height, and stability in the face of a powerful blow dryer. One of the things we observed was that different designs privileged one characteristic at the expense of another. A building that was particularly stable was also quite short. In Biology, we noted that this is characteristic of the natural world as well. An organism may have traits that make it well-adapted to one environment, while poorly adapted to another. We will revisit these concepts later this year when we cover evolution.

Tuesday, January 11, 2011

General Science and Biology: Which chip is the greasiest?

This week in science we asked the following questions: which brand of potato chip is the greasiest and more importantly, how can I be sure?

We went about answering them by carrying out 3 tests. The first 2 were a touch and a taste test in which the kids rated the chips on a scale from 1-5, with 5 being the greasiest. Then the kids were challenged to come up with a more quantitative test, one based on measurement. Some kids crushed equal amounts of each chip on a piece of graph paper and then compared the sizes of the different oil stains. Others compared the weight of the chips before and after crushing; the assumption being, the greasier the chip, the more oil lost in the act of being crushed on a piece of paper. Another test consisted of soaking different chips in water, removing them, and then comparing the amount of oil observed sitting on top of the water.

After carrying out our tests, we tested our tests. We read the nutritional information on the packages and reviewed our data to see which test was actually the best. Finally the kids thought about how they could improve their tests in the future.

Sunday, January 9, 2011

Physics: Stopping on a dime

This week the kids used their physics skills to solve an engineering problem: Say you want to build a new basketball court, how much room do you need, besides the court itself? To figure this out the kids collected data on their reaction time, running speed, and the distance you run past the finish line, as you try to slow down.

We decided to consider the slowest reaction time, the fastest speed, and the longest overshoot in order to come up with a safe and conservative estimate for the distance between the out-of-bounds line and other obstructions. The kids observed that most people can't stop on a dime, particularly not during a competitive sport like basketball, and based on our data suggested a minimum distance of 2.5 meters between the court and any walls or obstructions.

Friday, January 7, 2011

General Science: Observations of different white powders

This week we continued our exploration of physical and chemical properties by investigating 4 different white powders: sugar, salt, potato starch, and baking soda. The physical properties we investigated included: how each one looks under the microscope and how each one feels. As for chemical properties, we combined the powders with with vinegar and iodine and recorded the results. Finally we looked at whether any of the powders conduct electricity when dissolved in water.

The kids now have a comprehensive data sheet on these substances and their physical and chemical properties. If by chance, they should come into contact with some unknown white powder, making an identification should be a piece of cake!

One never knows when these skills and/or data might come in handy...