ROTATIONAL DYNAMICS
The dynamics of translational motion involve describing the acceleration of an
object in terms of its mass (inertia) and the forces that act on it: Fnet = ma. The
dynamics of rotational motion involve describing the angular (rotational)
acceleration of an object in terms of its rotational inertia and the torques that act
on it.
Rotational Motion
Previously, we covered objects that undergo circular motion. The next part of this
chapter focuses on taking an object and spinning it. Although we’ll have to take on
a new set of equations for rotational motion, we’ll soon discover that rotational
physics is analogous to the physics of linear motion, with different terminology.
For instance, an object’s mass measures its inertia, its resistance to acceleration.
The greater the inertia of an object, the harder it is to change its velocity. This
means it is harder to accelerate the object, which in turn means that the greater the
inertia, the greater the force required in order to move an object. Comparing two
objects, if Object 1 has greater inertia than Object 2 and the same force is applied
to both objects, Object 1 will undergo a smaller acceleration.
In the linear model we discussed motion in terms of force, mass, acceleration, and
velocity. When it comes to rotational kinematics, we need to change up a few of
these terms:
LINEAR KINEMATICS ROTATIONAL KINEMATICS
Force Torque (tau)
Mass Moment of Inertia (I)
Acceleration Angular Acceleration (alpha α)
Fnet = ma Tnet = I α
Velocity Angular Velocity (omega ω)