# Motion described by differential equations

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1. Nov 7, 2015

### diredragon

1. The problem statement, all variables and given/known data
Text from a classical mechanics textbook ( uploaded picture ) shows 2 diff equation describing the motion graphically presented in the uploaded picture. How were these set up?

2. Relevant equations

3. The attempt at a solution
I dont have a slightest clue as how are these equations derived in the first place.

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2. Nov 7, 2015

### Student100

They can be derived from the constraints on the system.

If it's moving on a plane, z is constant.
It's perpendicular to the plane.
It remains perpendicular to the plane.
And we can assume it's rolling without slipping.

You can re-derive everything from those four constraints.

3. Nov 7, 2015

### diredragon

So how exactly did they get to those two diff equations? The book just wrote them down. And its the first time im hearing about constraints, read it a while ago though...

4. Nov 7, 2015

### Ray Vickson

Please type out the equations; posting sideways-oriented photos will not bring you responses from most helpers.