To calculate the spring constant
A video that explains the whole manipulation for calculating the spring constant: measure with "tracker" and the use of OpenOffice. The spring constant is needed to make the experience of finding the mass of an astronaut in zero gravity.
It is possible to give this constant for students to save time in this case, simply suspend an "unknown" mass and measuring the period of oscillation to find the mass (see the relation between the periode and the mass.) If you use 2 springs with constant as k1 and k2, here's the formula. 

The Powerpoint presentation (like in the ebook and with the movie of the astronaut )


The Excel file for for the spring constant


Images with different forces on the spring
