Measuring Acceleration on a Bike using Phyphox

[haruspex]

and while still rolling, you should be able to get the static friction coefficient

Only by increasing the acceleration to the point where increasing it any further would lead to skidding. As I posted, that could be tricky.

 

[haruspex]

pushing the pedals with approximately the same force

The force applied to the pedals doesn't tell you anything useful.
How that translates into tractive force when not skidding depends on the gearing and wheel size. When skidding, you can increase the force on the pedals as much as you like without increasing the acceleration or the frictional force.
If both wheels are skidding or both are rolling, all you need to measure is the maximum linear acceleration, nothing else.

 

[berkeman]

I’m trying to calculate the coefficient of friction (μ)of different surfaces using a bike, where I can calculate the centripetal acceleration using an app.

OP -- sometimes when students try to come up with project ideas, those first ideas are fundamentally flawed. And in those cases, you should strive to see the flaws early and not spend lots of time on those paths and instead learn from the flaws and redirect to better paths.

Designing experiments to find the coefficients of friction involves focusing in on how best to find those coefficients. The classic tilted incline is one such experimental paradigm. Making precise force measurements in a horizontal test bed is another way to do it. Using a cellphone app to try to measure accelerations on a bicycle is not a way to do it, no matter how much work you try to do to shoehorn the friction measurement concept into a cellphone app that measures position as a function of time.

My recommendation would be to take a step back and think more about what you want to do. Since it is a project requirement to use that phone app in the project, think about other tests that you can do with it. If you still want to do friction measurements, you will need to find a better vehicle (sorry for the pun) for them. I don't see how to use the inclined plane paradigm with that phone app*, so you would probably need to think about some other way to demonstrate friction forces. You could try locking up both bicycle brakes in a skid and using the app to measure the deceleration, but that will only work for hard smooth surfaces that don't deform, and will only give you values for dynamic friction and not static friction.

Sometimes you have to step back and realize that the initial path you've chosen for a project is flawed, and revise your plan.

*EDIT/ADD -- Maybe you could use the app to measure the speed of the mass going down the incline after it breaks loose to determine the dynamic friction coefficient...

 

[OmCheeto]

That’s strange as my graph only took a few data points, your’s far more detailed than when I exported the data to files on my phone, I’ll give it a shot exporting it to my phone. Yes I suppose there are a lot more factors that influence the accuracy of results, however as I have to write a formal investigation, I’ll include that in the observations section. Hopefully the centrifugal acceleration sensor is more accurate if I export it. When I manage to record the data on a few surfaces I’ll add a few images so you can see if they improved.

I look forward to it! Per forum rules, I can't share my findings, as that would be kind of like solving your homework problem. I've learned a lot in the last 12 hours, fiddling with and looking at my data. If I were you, I'd write that into your paper, regarding the stumbling blocks which lead to a more refined experiment.

ps. Here's the results of my back wheel coast down experiment from this morning:

acceleration without gravity mode

I haven't started analyzing it yet, but it sure looks different.