Class 10 09 - calarts/calarts.github.io GitHub Wiki
schedule
- review last weeks' lab results
- lab (4-5:30)
- presentations (5:30-7)
Lab 2: terminal velocity, hydrophobic surfaces, speed of sound
We can calculate the terminal velocity of a mass from its mass and surface area.
EXPERIMENT 1
Does the mass of balls held aloft by a stream of air show up in the force being applied by a jet of air produced by a fan? We assume that it WOULD NOT register on a scale supporting the fan.
EXPERIMENT 1.5
RP: How much air power is needed to hold a fairly big rock to float in a room?
Does the terminal velocity of a mass change when the surface area is increased? Measure the terminal velocity of a ball dressed first with a glossy surface and second with a furry surface. We predict that the furry surface will have a lower terminal velocity.
things to try
Let's find two balls with equal mass and dress one up with a complex surface to see how much resistance/lift that would provide.
EXPERIMENT 2
NS: A material with a high enough coefficient of friction will be hydrophobic and decrease the surface area of contact with a water droplet.
We assume that a dry surface exerts a higher static (friction) force on a plane than a wet surface. Measuring dry first then wet. Compare the numbers.
How does the NeverWet change the surface of the brick? Is there some way that we could see that or get a closer look at it? How could the interaction microscopic surfaces between water, NeverWet be made more accessible to us?
confocal laser microscopy offer a promising approach; I have an email in to a student at MIT who is working on a DIY rig. Meanwhile, how might we investigate the surface without using optics? Exaggerate the qualities of the surface
things to try
- Amplify a cat's whisker scratching the surface => audio file, visible trace
- Compare the static friction index to known surfaces (example: brick w/o coating)
EXPERIMENT 3
YL: Due to differences in the atmosphere, would sound travel faster or slower on Mars than on Earth?
We saw that familiar sounds come out differently after traveling through Helium. How would the atmosphere of Mars alter sound? Can we make any good guesses based on what we found in Helium?
The atmosphere on Mars is composed 95.9% of carbon dioxide. The pressure measures about 600 pascals (0.087 psi), about 0.6% of Earth's mean pressure at sea level pressure.
Here's a table: Speed of Sound for air and CO2
| Gas | Speed of Sound meters/sec (ft/s) |
|---|---|
| Air | 331 meters/sec (1086 ft/s) |
| Carbon Dioxide | 259 meters/sec (850 ft/s) |
questions
- can we simulate Mars' atmosphere in the classroom?
- if not, could we calculate the sound of the audio based on the Helium lab?
presentations
illustrations
5-7 minutes should do it.
| Title | Due | Who | Labels |
|---|---|---|---|
| Pencil lead/chalk/markers : does the writing stay on the paper due to friction? Adhesion? Magic?? | 10/9/13 | JV | illustration |
| What keeps felt fabric held together? | 10/9/13 | LF | illustration |
| What makes silk so strong? | 10/9/13 | CL | illustration |
| What is the process of creating natural dyes and how does the effect and process differ from synthetic dyes? | 10/9/13 | LF | illustration |
| How does fabric dye work? | 10/9/13 | GD | illustration |
calculations
Please create an iPython notebook page and define variables for each calculation.
| Title | Due | Who | Labels |
|---|---|---|---|
| How can we measure the gravitational pull of the moon within a living things body? | 10/9/13 | SB | calculation |
| Can I use canvas as a conductor? | 10/9/13 | WM | calculation |
| Is fabric stronger when it is wet or dry? | 10/9/13 | LF | calculation |
| Can we measure the gravitational pull of the moon within a living things body? | 10/9/13 | SB | calculation |
speculations
Let's work out an experiment or experiments from these speculations. Start with a clear statement of the hypothesis, develop a falsifiable statement, and then sketch out the experiment.
| Title | Due | Who | Labels |
|---|---|---|---|
| How do those materials that we "absorb" affect the body (positively/negatively)? | 10/9/13 | RG | speculation |
| What causes the fibers of a cloth to shrink after drying and washing? | 10/9/13 | LF | speculation |
| Why is salt needed when dying fabric? | 10/9/13 | LF | speculation |
| How and why does the sun fade fabric? | 10/9/13 | JK | speculation |
| What makes carbon fiber conductive? | 10/9/13 | DR | speculation |
| Communication through "two cups and a wire". What materials make this possible? What materials don't work and why? (Certain materials in mind were paper vs plastic vs metal cups. String vs wire.) | 10/9/13 | YL | speculation |