Odds & Ends
“There is no authority who decides what is a good idea.” - Richard Feynman
ESL: English as a Science Language (or the astrophysics of love)
My British, English-teaching colleagues offered me a seat on an interdisciplinary field trip to the Ekamai Planetarium in Bangkok. I accepted. I belatedly realised that nothing is free in life: being a Science teacher, whose mother tongue wasn't English, I was naturally delegated to design an English assignment for our students reflecting on the trip.
Below is the assignment and the anonymised student's writeups on it.
Hydroelectric Dams - what can be cosier?
Hydroelectric dams and its power plants, especially when contrasted with smoke-spewing coal-fired power stations, look clean and benign. The operators are quick to emphasize the benefits of hydroelectricity and its absolute and unquestionable environmental friendliness. But how (and why) can they be so sure?
Senior science students were asked to become Investigative Journalists during their residential trip to the Rajjaprabha Dam and Cheow Lan Reservoir near Surat Thani, asking tough, inconvenient questions and not taking a ‘no’, or even a 'maybe', for an answer.
Background, investigative template, research topics and examples of anonymised student’s reports below.
Most everybody likes rocketry, but explaining how and why rockets work is a bit tricky. It involves the conservation of momentum principle and the idea that a momentum of an objects can be only changed by an impulse. To make things even more complex, they are both vectors which means that direction matters.
Using ethanol-propelled pop-bottle rockets to demonstrate the concept is a fun class experiment which, in addition to physics, introduces the chemistry of rocket fuels and teaches a number of lab manipulative skills while reinforcing lab safety precautions. Having access to digital force gauge loggers with sufficient sampling rate (ours were capable of some 100 samples per second) allows for more advanced exercise where the rocket thrust is recorded as a function of time and the result is integrated to calculate the impulse that, when equated to rocket's momentum, allows for calculating its velocity while showing the propagation of experimental uncertainties. A natural class differentiation...
Mr. Maciej's Honda CRF250L Speedometer Calibration
Instrument calibration curves explained - accounting for non-linearity and random and systematic errors. Student's instructions here.
All in all it turns out that my Honda's speedometer overestimates the the real speed by some 8-9% (TrueSpeed=0.92*SpeedometerReading). The instrument error is by and large systematic and proportional to the speedometer's readings. Car and motorcycle speedometers reading too high are quite common mostly for legal liability reasons.
Update: I have changed the font drive sprocket to a smaller one (13T) which further increased the discrepancy between the speedometer reading and the true speed to some 15% (but the motorcycle is more responsive now...).
Exponential Decay of Beer Froth (really!)
When I read about this IgNoble prize in Physics I couldn't believe my luck - what can be better than combining Science with pleasure and explain a concept of non-linear radioactive decay and half-life to my students in the process?
The lesson uses the measurements of the rate of decaying beer froth bubbles as an analogy for a radioactive decay of carbon C-12 isotope and explains its applications to the dating of fossils. Students estimate the half-life of their group's brand of beer and compare it with those of their schoolmates, taking into account the uncertainties of their measurements. Who said that Science can't be fun?
Refraction of water ripples in Mr. Maciej's swimming pool
Illustrating wave fronts and the refraction of the progressive wave travel direction as a result of wave speed change due to abrupt decrease of water depth (medium) at the edge of the pool.
The speed of water surface waves (celerity) depends on water depth in the deep pool and the wavelength of the wave when it shoals. Read more here and here, compute the water wave speeds here, and learn how the wave speed equations are used to explain the destructive power of Tsunamis (also here).
Confluence of Physics and Physical Education
This is a teaser of an aerial movie, shot using a DJI Phantom 4 drone.
Drones became more affordable lately and are so easy to fly, with their gyroscopic camera gimbal stabilization so refined, that such feat can be now accomplished by a newbie drone pilot (me) after just a few hours of flight time.
Martian Challenger (or did The Martian movie get the science right?).
I agree with Neil deGrasse Tyson that Scott Ridley made a remarkable effort to get the science in the movie right, but it's still fun to look a little deeper and use some math to see what's possible, what's unlikely and what's plainly wrong.
Watch the movie, then take the Challenger below! You don't need to be as brave or resourceful as Mark Watney, just realistically evaluate the science in it!
Science Fairs (or a love-hate relationship)
Science Fairs have a spotty reputation among students and their parents. Schools promote them as 'fun', 'real-life' and 'scientific', but they also can occasionally be (and have been) utterly anti-inspirational, unfair or plainly boring.
I'm firmly split on the topic, but I also firmly support well-done science fairs (or weeks, or days...) that can cut through the boredom and daily grind of science classes, bring out amazing projects and demonstrations that are not easy to experience elsewhere, involve communities, connect the dots, and let people experience real, creative and relevant science that they are interested in (not just hear about someone else trying it).
Science Fairs may be immortal, but they are a lot of work that can be satisfying... Below are some examples - perhaps not ideal, but nothing is. You're the judges....