There are rotational equivalents to the rules of linear dynamics,
and rotational equivalents to the linear quantities
described by those rules.
Work done by a linear force is Work = force * distance;
in the rotational world, work is done by a torque applied
through some angle:
work = (torque) * (angle)
Translational kinetic energy is KE = 0.5 * mass * speed^2;
in the rotational world, kinetic energy depends on the
moment of inertia of a body, and its angular speed:
rot KE = 0.5 * (moment of inertia) * (angular speed)^2
If a body rolls down a hill, it must split the gravitational
potential energy it loses into two pieces: a translational
KE and a rotational KE. That means that it must have less
translational energy than an object which just slides.
So rolling objects move more slowly than sliding ones,
all other things being equal.
