01-14-2021, 04:16 PM
(This post was last modified: 01-14-2021, 04:17 PM by Sebastian Staacks.)
(01-14-2021, 03:10 PM)solid Wrote: Mount your wheel horizontally .. Row accelerometer measures \vec{a} - \vec{g}.
That would be my guess, too. However, the centripetal acceleration experiment does not use the raw sensor but the accelerometer "without g" (aka linear acceleration). This is supposed to subtract the gravitational contribution and in theory it should not show this behavior. In practice, the device cannot do this perfectly and it will depend on the phone how well it can compensate the force of gravity on the sensor. Some device do this near perfectly while others have trouble in specific situations. If you start the measurement while the wheel is already spinning, please try starting the experiment while the wheel is at rest as some devices take a reference vector when starting which fails if it is already spinning.
Besides that phyphox tries to help a bit by averaging the acceleration over 0.5s, but as this time window will shift over the oscillation without perfectly matching a period, there will still be an oscillation as a result. it might be interesting to see what the acceleration looks like when recorded with the simple "acceleration without g" configuration as this will not average the data.