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Static Friction Coefficient - Printable Version

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Static Friction Coefficient - chcheyin - 08-30-2020

Hello!
Thank you so much for inventing this great app, and providing awesome tutorial videos!
I am a high school teacher and I want to introduce this app to students recently.

This experiment is what I want to introduce:
https://www.instagram.com/p/CAc2re5ANTX/?utm_source=ig_web_copy_link

But  instead of make the block sliding down, I prefer to let  my cellphone slides down itself.
And at the instant when sliding begins , The phone can record the inclination angle of that instant automatically then stop recording.
To achieve this , I will need to combine these two sensors :
acceleration with g (for inclination meter)
acceleration without g (for motion detector)

I wish to modify the Motion Stopwatch and Inclination that app already has by editing them on the editor. 
But after trying for two whole day, I realized that is not an easy task. Confused

Can I make a wish for a project like it?
Thank you!

Beste regards
CheYin


RE: Static Friction Coefficient - Jens Noritzsch - 09-01-2020

Unfortunately I have had no time yet to look into it. For the sake of clarity, adapting the motion stopwatch so that it shows an inclination rather than/next to the time would be fine?


RE: Static Friction Coefficient - chcheyin - 09-03-2020

(09-01-2020, 08:53 PM)Jens Noritzsch Wrote: Unfortunately I have had no time yet to look into it. For the sake of clarity, adapting the motion stopwatch so that it shows an inclination rather than/next to the time would be fine?
Thank you for your kindly reply!
I will try this method in next few days!


RE: Static Friction Coefficient - SJS - 09-04-2020

Dear CheYin,

in a workshop we have created a very quick-and-dirty version of this experiment. Therefore I cannot recommend this experiment without reservation, because it is not proper for the following reasons:

It is limited to the maximum angle from the moment the motion stopwatch is triggered (lines 164-167). Assuming that the angle is increased during the slide, the increased angle is used in the further calculation and not the angle from the moment of triggering. Therefore the angle must not be increased from the moment of slipping.
Regarding the triggering: the if-query (lines 157-162) only asks if the timer of the motion stopwatch is running; this means that as soon as the motion stopwatch takes a time measurement (even a later one!), the corresponding angle is always measured as well, although it seems as if the measurement has already been finished.
Therefore it is possible to start another measurement unintentionally; for example, if the smarpthone already slipped from the inclined plane, a new measurement can be started unintentionally when lifting (= new acceleration) and a different angle could be processed (cp. if-query). This means that the measurement must be stopped via the ||-button before the smartphone is lifted.

So please use the attached file with some caution. It would be much more elegant to store and process an angle for each activation of the trigger.

Best wishes, Sebastian.

PS: i assumed the same as Jens, that the motion stopwatch should show the angle instead of the time.


RE: Static Friction Coefficient - Roland Van Kerschaver - 09-09-2020

Put a matchbox on a horizontal iPad.
Start Motion stopwatch + Inclination.
Empty the garbage box.
Incline the iPad till the matchbox begins to slide.
Do not change the inclination.
Stop Motion stopwatch + Inclination
Note the static friction coefficient.
Reset

Repeat this 5 times.


RE: Static Friction Coefficient - chcheyin - 09-12-2020

(09-04-2020, 06:07 PM)SJS Wrote: Dear CheYin,

in a workshop we have created a very quick-and-dirty version of this experiment. Therefore I cannot recommend this experiment without reservation, because it is not proper for the following reasons:

It is limited to the maximum angle from the moment the motion stopwatch is triggered (lines 164-167). Assuming that the angle is increased during the slide, the increased angle is used in the further calculation and not the angle from the moment of triggering. Therefore the angle must not be increased from the moment of slipping.
Regarding the triggering: the if-query (lines 157-162) only asks if the timer of the motion stopwatch is running; this means that as soon as the motion stopwatch takes a time measurement (even a later one!), the corresponding angle is always measured as well, although it seems as if the measurement has already been finished.
Therefore it is possible to start another measurement unintentionally; for example, if the smarpthone already slipped from the inclined plane, a new measurement can be started unintentionally when lifting (= new acceleration) and a different angle could be processed (cp. if-query). This means that the measurement must be stopped via the ||-button before the smartphone is lifted.

So please use the attached file with some caution. It would be much more elegant to store and process an angle for each activation of the trigger.

Best wishes, Sebastian.

PS: i assumed the same as Jens, that the motion stopwatch should show the angle instead of the time.


Thank you! Sebastian and SJS!
I have tried the file. It was awesome! Thank you for responding my demand.

Although my wish was that motion stopwatch could stop taking time measurement after being triggered (when the phone start to slide)
,the file you made for me is sufficient to accomplish my desire!

I will try to adjust the motion stop watch to show the angle instead of the time in future!
Thank you so much!