Glossary

angular acceleration

the rate of change of angular velocity with time

angular momentum

the product of moment of inertia and angular velocity

change in angular velocity

the difference between final and initial values of angular velocity

kinematics of rotational motion

describes the relationships among rotation angle, angular velocity, angular acceleration, and time

law of conservation of angular momentum

angular momentum is conserved, i.e., the initial angular momentum is equal to the final angular momentum when no external torque is applied to the system

moment of inertia

mass times the square of perpendicular distance from the rotation axis; for a point mass, it is $I={\text{mr}}^2$ and, because any object can be built up from a collection of point masses, this relationship is the basis for all other moments of inertia

right-hand rule

direction of angular velocity ω and angular momentum L in which the thumb of your right hand points when you curl your fingers in the direction of the disk's rotation

rotational inertia

resistance to change of rotation. The more rotational inertia an object has, the harder it is to rotate

rotational kinetic energy

the kinetic energy due to the rotation of an object. This is part of its total kinetic energy

tangential acceleration

the acceleration in a direction tangent to the circle at the point of interest in circular motion

torque

the turning effectiveness of a force

work-energy theorem

if one or more external forces act upon a rigid object, causing its kinetic energy to change from ${\text{KE}}_{\text{1}}$ to ${\text{KE}}_{\text{2}}$, then the work $W$ done by the net force is equal to the change in kinetic energy