Summer 2009 Questions and Resources
Alfredo sends this link to a movie of a railroad tank car imploding.
The square of electricity
Force, Field,Potential Energy, Potential
The beinners guide ot aerodynamics, A great online book from NASA,
Bob Miller's Light Walk http://www.exploratorium.edu/light_walk/lw_main.html
Here are some light activities
Peel a CD, cut the aluminizing off a compact disk to make a transmssion diffraction grating.
Color Diffraction Grating
Image on a Mirror
Fresnel lens and Laser
Scan a Laser through a lens
Laser CD, reflect a laser off a CD to measure the line spacing of the
Laser Light, Explore the properties of laser light.
Laser Milk, Laser light scattered through milk produces a 3-d time varying interference pattern
Light Box, build a simple box to explore image making
Poisson Spot, make one with a pointer laser and a BB
Ray Tracing, How to do it
Audacity is a free sound recording program with spectrum analysis and automatic musical note identification.
Here are the notes from an Audacity workshop.
San Francisco 1906 earthquake movie http://earthquake.usgs.gov/regional/nca/1906/simulations/classroom.php
Seeing Yellow (Disagreeing about color) the Snack pdf format an article by Gorazd Planinsic.
The spectra of the elements
Paper Tape Timer reference, mathematics: http://www.exo.net/~donr/activities/Paper_Tape_Motion_Timer.pdf
Air resistance force calculation. Why is air friction proportional to v^2 for turbulent airflow.
Information about human senses:
Howard Hughes Medical Institute, Seeing Hearing and Smelling the world.
A great source of physics information
Hyper Physics http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
A new source of physics data. Wolfram Alpha http://www67.wolframalpha.com/
and for the thermal expansion http://www67.wolframalpha.com/input/?i=thermal+expansion
Men carrying a door between two people videos:
Find the Highest Note
Laser Speckle explanation
We purchase our colored filters from Holtz-Muller theater supply in San Francisco, #415-826-8383
They are $6.50 per sheet, 20 x 24 inches
TI uses Roscolux Medium Red #27
Roscolux #80 Primary Blue, and
Lee Filters #139 Primary Green.
Mix and Match
Add R G B to make other colors
From educational innovations
From Project Star
Air resistance F = kv vs cv^2
For laminar flow the force from air resistance is proportional to the velocity.
For turbulent flow it is proportional to velocity squared.
A bicyclist travelling at velocity v in still air experiences air friction that increases as the velocity of the bicyclist squared. F = cv^2
Let's do a simpler problem first the bicyclist colldes with a beanbag of mass m. As viewed by the bicyclist the beanbag is mving towards them and has kinetic energy E = 0.5mv^2 which goes to 0 in the inelastic collision with the byciclist. So in the inelastic collision between beanbag and bicyclist the bicyclist must do work on the beanbag to bring it to rest. The work done will be 0.5mv^2. Work is force times distance. So the force of hitting one beanbag depends on the distance over which the beanbag is brought to rest. 0.5mv^2 = F d.
Now consider a beanbag every metre, d = 1m. And calculate an average force by assuming it takes the full meter to stop the beanbag.
F = E/d = 0.5 mv^2 = Fd so F = 0.5mv^2/d
Consider air of density p moving at velocity v colliding with an object with a front surface area A.
The air comes to rest when it strikes the object. The mass of air is pV where V is the volume of air that hits the cyclist.
So the kinetic energy, E,of the air is 0.5mv^2 = 0.5 pVv^2 now the volume of air is Ad so we get
E = 0.5pAdv^2
and F = E/d = 0.5 pAv^2
the air resistance force is proportional to the density of the air, the area of the bicyclist and the velocity of the bicyclist squared.
Scientific Explorations with Paul Doherty
22 June 2009