Very nice! I tried it with just a rubberband holding a bucket. Just wind it up, put the phone in the bucket, start the experiment and let the rubberband unwind. It gives the same accurate graph but without the need for a salad spinner.
Sounds simple and clever. Just to be sure, that I understand your setup correctly: The bucket is suspended from the rubber band and rotates about the axis of the rubber band, so the radius of the rotation ist just the radius of the bucket?
Yes exactly. I tried it with a bicycle and a desk-chair first but then the acceleration was not very controlled. With the rubberband in the centre of the holder of the bucket and then winding the combination up far enough (until it started hurting my finger), it delivered a perfect graph. The acceleration goes very smooth. After winding it up I placed the phone in the bucket, started the experiment on the phone and let the rubberband unwind. The radius of the bucket is then the radius of the rotation as well indeed. I watched some of your other videos as well, very interesting and a great app!
Well, maybe someone comes up with a fancy way to measure it with the app. One could track the progress of the sun using the magnetometer as a compass or one could set up some fancy way to measure the rotation of a Foucault pendulum. But if you want to measure Earth's rotation directly, the answer is "no". It is just too slow. It does a full rotation every 24h (not exactly, but that's close enough for an estimate), so we have an angular velocity of 2*3.14/24/60/60s=0.000073rad/s. The phone measures rotation using the gyroscope and on my Pixel 3 it has a noise in the order of 0.003 rad/s, which is worse by two orders of magnitude. Maybe there are phones with slightly better gyroscopes and maybe you can eliminate some of the noise by averaging (after all, Earth's rotation is very steady), but even then, the phone's internal recalibration methods would eliminate the rotation from the data.
nice video but i need to input the data i got from the square plot to centripetal formula (Fc = m.ac ) but i don't have any idea how to choose one plot that represent the graph i have to the formula. thanks in advance
You could zoom into the graph by tapping on the two wedges at the top left of it. Then you could pick any individual data point or export the full dataset via “More tools”.
Acceleration graph: the angular velocity is on the x-axis being a measure of how quickly the salad spinner rotates, the acceleration on the smartphone is on the y-axis indicating the force (proportional to the acceleration) that is required by the edge of the salad spinner to keep the smartphone on track. The higher the angular velocity the higher the acceleration is. The square plot graph proves that the mathematical relationship is quadratic, i.e., acceleration ~ (angular velocity)². HTH.
Technically, it is a matter of the reference frame: centripetal (commonly used in schools) from the point of view of the resting outer case of the salad spinner or centrifugal in the rotating system of the smartphone.
The automatic English subtitles appear to be not too bad. After selecting these, you are offered automatic Portuguese subtitles in the settings then. As legendas automáticas em inglês não parecem ser muito más. Depois de as seleccionar, ser-lhe-ão então oferecidas legendas automáticas em português nas definições. - we hope this translation makes any sense… ;)
Very nice! I tried it with just a rubberband holding a bucket. Just wind it up, put the phone in the bucket, start the experiment and let the rubberband unwind. It gives the same accurate graph but without the need for a salad spinner.
Sounds simple and clever. Just to be sure, that I understand your setup correctly: The bucket is suspended from the rubber band and rotates about the axis of the rubber band, so the radius of the rotation ist just the radius of the bucket?
Yes exactly. I tried it with a bicycle and a desk-chair first but then the acceleration was not very controlled. With the rubberband in the centre of the holder of the bucket and then winding the combination up far enough (until it started hurting my finger), it delivered a perfect graph. The acceleration goes very smooth. After winding it up I placed the phone in the bucket, started the experiment on the phone and let the rubberband unwind. The radius of the bucket is then the radius of the rotation as well indeed. I watched some of your other videos as well, very interesting and a great app!
Happy you like it and thanks for this alternative setup. I will certainly try it!
Good.
great video, please do more of them!!!
Very nice , how do you read the Graphics?
Check out the answer to Liko Liman below. HTH.
What does the slope of the square plot represents ?
The constant of proportionality is the radius: the formula for the centripetal acceleration is a = r × ω²
Nice.
Can this app be used to measure Earth's rotation? If not, why?
Well, maybe someone comes up with a fancy way to measure it with the app. One could track the progress of the sun using the magnetometer as a compass or one could set up some fancy way to measure the rotation of a Foucault pendulum.
But if you want to measure Earth's rotation directly, the answer is "no". It is just too slow. It does a full rotation every 24h (not exactly, but that's close enough for an estimate), so we have an angular velocity of 2*3.14/24/60/60s=0.000073rad/s. The phone measures rotation using the gyroscope and on my Pixel 3 it has a noise in the order of 0.003 rad/s, which is worse by two orders of magnitude. Maybe there are phones with slightly better gyroscopes and maybe you can eliminate some of the noise by averaging (after all, Earth's rotation is very steady), but even then, the phone's internal recalibration methods would eliminate the rotation from the data.
nice video but i need to input the data i got from the square plot to centripetal formula (Fc = m.ac ) but i don't have any idea how to choose one plot that represent the graph i have to the formula. thanks in advance
You could zoom into the graph by tapping on the two wedges at the top left of it. Then you could pick any individual data point or export the full dataset via “More tools”.
How to read the graphsM
Acceleration graph: the angular velocity is on the x-axis being a measure of how quickly the salad spinner rotates, the acceleration on the smartphone is on the y-axis indicating the force (proportional to the acceleration) that is required by the edge of the salad spinner to keep the smartphone on track. The higher the angular velocity the higher the acceleration is. The square plot graph proves that the mathematical relationship is quadratic, i.e., acceleration ~ (angular velocity)². HTH.
Super App, Super Video👍
Muy bueno
Centripetal??
Technically, it is a matter of the reference frame: centripetal (commonly used in schools) from the point of view of the resting outer case of the salad spinner or centrifugal in the rotating system of the smartphone.
Legendas em português por favor 🙏🏻
The automatic English subtitles appear to be not too bad. After selecting these, you are offered automatic Portuguese subtitles in the settings then.
As legendas automáticas em inglês não parecem ser muito más. Depois de as seleccionar, ser-lhe-ão então oferecidas legendas automáticas em português nas definições. - we hope this translation makes any sense… ;)