How many seconds does it take for a "car" to turn a certain amount of degrees? *math*?

If the outer wheel in the turn doesn't slip, then the time to turn can be calculated.

Time for one revolution of the wheel = 1 / 2.25 = 0.444 seconds.

Distance covered by wheel in one revolution = 2 pi r = 6.9115 inches.

Distance needed for a 360 deg turn = 2 pi R = 2 pi 6.875 = 43.1969 inches.

Wheel revs needed for a 360 turn = 43.1969 / 6.9115 = 6.250 revs.

Time for that many revs = 6.250 * 0.444 = 2.778 seconds.

Time for each degree = 2.778 / 360 = 0.00772 seconds.

But ... in real life, there will always be some slip, and the amount depends on speed and the condition of the wheels and surface. That's why it's better to have some method to sense the direction of your robot. Maybe a gyro system, but those drift over even a few minutes. A magnetic compass doesn't drift, but is affected by speed and vibration. There are ways to combine them to get the best of each, see the second link below. Takes a lot of software.

Using Unit Cancellation:

Formulas:

Circumference of a circle = 2𝛑r

For degrees for a given time:

X seconds ( 2.25 RPS wheel revolutions/second) ( 2𝛑 *1.1in /wheel rev) (360 degrees/(2 𝛑 6.875 inches))

= ____ degrees

So simplified down:

(X seconds) (129.6) = _____ degrees

Or for time for degrees just take inverse:

(x degrees) /0.007716049382716 = _____ seconds