RSA 4

RSA 3

RSA 2

RSA 1

Mobile in the Physics' Lab

A pen without refill is more or less a lambda/4 resonator (i.e. a pipe closed at one end and opened at the other). If you blow in the pipe and observe the spectrogram of the so produced sound, you'll measure the standing wave's frequencies.
 
The pen I used (a bic) is 13.3 cm long.

The predicted frequencies are:
f0= 639 Hz; f1=1917 Hz, f3= 3195 Hz, f4= 4473 Hz

The measured frequencues are:
f0= 578 Hz; f1= 1758 Hz; f2= 3181 Hz.

Kinematics of Felix Baumgartner's Jump

Today we have collected datas from the video of Felix Baumgartner's jump (http://www.youtube.com/watch?v=Xe7TKEAa_24). Here the results of our analysis.
Unfortunately we have speed datas only after 21s from the beginning. From our graphs we have calculated Felix's acceleration from the 21st second to the 26th of the motion (the slope of the line).
It's 8.7 m/s2 (up there gravity is slightly smaller. But drag is also at work, I guess).

Integrating this datas we can have displacement vs time, derivating we can calculate acceleration .

The equation of a smile

Polynomials! As we learn that stationary points of a polynomial are the zeroes of the first derivative, we can easily understand that if we want a polynomial to oscillate very much we must increase it's degree.

A fun activity to show this is finding the equation of a curly smile. In the photo I've done this with the smile of  a cat. In the classroom each student can find his own equation.