Why is the shape of an object not considered in motion on an inclined plane?

[Deepak K Kapur]

While deriving formulas/describing motion on an inclined plane, why don't we take into account the shape of the object undergoing motion?

e.g.
1. If I take an inclined plane and place a ball on it, only a small amount of inclination would make the ball move down the plane...

But...

2. If a take a matchbox and place it on the inclined plane, a lot of inclination would make it move down...

Why aren't such factors taken into account?

 

[Vatsal Sanjay]

We do take those factors into account. See toppling.

 

[Simon Bridge]

I don't know about you, but "we" always take into account the shape of the object.
When you are being taught how to work out equations of motion, you are taught only the simplest cases - then gradually more complicated cases, until you are good enough to cope with the really hard cases.

 

[Dale]

Why aren't such factors taken into account?

They are when they matter. Often in introductory classes we use scenarios (like a frictionless inclined plane) where such factors are irrelevant or deliberately idealized. This is not an indication that those factors cannot be taken into account, but just a way to simplify learning and avoid overwhelming students all at once.

 

[Deepak K Kapur]

Thanks a lot...everyone.