Why do spheres roll easier than cubes?

[Sundown444]

I am aware that this could be the wrong section for this, but I wish to ask this here if you all don't mind. You all know how a sphere rolls along the ground easier than a cube, right? Well, how are the physics of motion involved in why a sphere rolls easier than a cube, or an irregular object?

 

[pbuk]

When a sphere rolls its centre of mass stays at a constant height above the surface.

 

[Sundown444]

When a sphere rolls its centre of mass stays at a constant height above the surface.

What about other shapes?

 

[pbuk]

It doesn't (apart from a cylinder and similar shapes).

 

[Sundown444]

It doesn't (apart from a cylinder and similar shapes).

Well, if that is that, then thanks. I appreciate the help.

Wait, in the case of both spheres or other objects, the CoM still follows a straight line, right?

 

[pbuk]

Yes I guess that's it - there's not much more to say really, except that moving the centre of mass of say a cube up and pivoting it around an edge takes energy; some of this energy is released when the cube "falls" over the pivot edge but then that most of that energy is lost in heat and perhaps sound when the cube lands on a face, then you have to put more energy into lift the centre of mass again...

 

[Sundown444]

Yes I guess that's it - there's not much more to say really, except that moving the centre of mass of say a cube up and pivoting it around an edge takes energy; some of this energy is released when the cube "falls" over the pivot edge but then that most of that energy is lost in heat and perhaps sound when the cube lands on a face, then you have to put more energy into lift the centre of mass again...

And there is less energy to be used in a sphere, right?

 

[pbuk]

Only what is lost in friction.

 

[Sundown444]

Okay then. I get it now. Thanks.