I'm participating a challenge that requires me to try and discover the mass of a person based on its fall time.
The rules are as follows:

* You must use a smartphone
* You can't use any additional hardware besides the ones inside the smartphone

My first attempt was to read the phone's accelerometer constantly and check the vector sum of the acceleration of X, Y and Z. Based on the numbers produced by this equation I'm already able to detect if the phone is falling and when exactly it collides with a plane. Woot!

I need to do the same thing but with the smartphone on my lap and sitting on a traditional office chair. When I press the chair height knob, I should capture the starting and collision moments (unix timestamp) and based on that difference of milliseconds the challenge asks to come up with an approximation of the mass in kg of the person using the app.

Is there a way to discover the mass of a body based on its "falling time" like described above? I've been searching for this in the internet but all I was able to find was methods of discovering the distance traveled based on mass and velocity.