Applying math to real world problems

[OmCheeto]

:( the worst thing about talking to people about a topic you have no clue about is you have no idea when you're being trolled :(

We will let you know when we start trolling you.

As to your spinning penny, I have no interest in solving the problem, as I see little "real world" use of the answer. (How long will it take a 300 kg generator to spin down with a coefficient of friction x, radius y, length z, once motive power is removed with no load? My answer: Who cares)

You might go to the physics or homework section and request guidance on how to solve the problem. Off the top of my head, you will need to know the following:

Mass of the penny
Initial angular velocity
(Some basic knowledge of Rotational Dynamics: Halliday & Resnick, 2nd Edition, Revised Printing, 1986, page 198)

From here you would measure the amount of time it takes for the penny to stop spinning.
This would yield, mathematically, a deceleration rate.
From that, I believe you could determine the coefficient of kinetic friction between the penny and your surface.

Then, with some mathematical knowledge of physics, you could extrapolate an equation which relates time, angular velocity, mass, etc.

Actually, I wouldn't solve the problem for you even if I found it to be a useful bit of knowledge. It's not allowed here.

 

[BobG]

As to your spinning penny, I have no interest in solving the problem, as I see little "real world" use of the answer.

Obviously, you should have picked a more interesting problem, such as:

If you spin a class ring, why does it almost always to seem wind up spinning with the jewel part on top?

(And there is an obvious answer why the jewel part has to wind up either directly on top or directly on the bottom, but only a slightly satisfying answer why it has to wind up on top.)