Values of the acceleration

[Mamboleoo]

Hello,
I'm currently working on a lesson for my computer science class with my students to explore all the sensors available in a phone.
I'm trying to understand how the acceleration values from my graph.
My experiment is to drop my phone from 1.5m up and to check the values of the acceleration.
In attachment you cans see I'm having two high positive values that are matching the two falls from different heights (second one is higher).

My question is why is my phoning detecting a positive acceleration of >60m/s² as the phone shouldn't really accelerate more than the gravity (9.81m/s²).
From what I concluded, the high value corresponds to when my phone hits the ground (blanket), but why does the phone captures an acceleration.

Sorry if this is more of a general science question than about the phone, but I'm having trouble understanding the results here.
Thank you for your help!

   

[Jens Noriʇzsɔɥ]

The free fall segments can be perfectly seen in the yellow z graph. Apparently, you held the smartphone in your hands with the screen upwards before letting it drop. Let‘s come to the reading of about 10 then later. (BTW, the coordinate system is shown at https://phyphox.org/sensors/)

The two periods of time where the acceleration drops to zero is when the smartphone falls. In free fall, everything inside the smartphone does not experience any forces so the sensor reading is zero (I have not quickly find a better video than https://www.pbs.org/video/fire-in-freefa...nt-eil0iz/). You might have experienced this on fairground rides: if you lose contact to the seat, for instance on a free fall tower, you feel weightless. We might see some effect of air resistance slowing down the smartphone to the end of the free fall with the z acceleration apparently slightly increasing.

The impact on the ground leads to a rather abrupt deceleration (acceleration in the opposite direction). Accordingly, you notice these high values in the reading: huge speed change in a short time, opposed to the direction, so positive z. I cannot definitely tell, if the impact is really harder after the second fall as some might have been picked up by the other axes. The accelerations in the „absolute“ tab might be much closer to each other.

Now, why does the z-axis show about 10 when the smartphone is resting on its back: the sensor cannot tell if the smartphone is accelerated with 1g upwards or if it is experiencing a gravitational force. If you were lying in a box that is accelerating with 1g in the direction of your head, your body also couldn‘t tell if you are lying or standing on your feet: it‘s the same feeling in your back and in your feet.

[Mamboleoo]

Wow thank you so much for those clear explanations!
I cannot wait to try it with my students