Rotational Motion Practice Flashcards

This set covers key concepts and definitions from Lecture 8 on Rotational Motion, including speed, inertia, torque, and centripetal forces.

Translational motion

Motion along a straight line.

Rotational speed

A measure of how quickly or slowly something rotates about an axis, represented by the lowercase Greek letter omega $\omega$.

Degree measure of rotation

A measure where one full rotation is equal to $360^{\circ}$.

Radian measure of rotation

A measure where one full rotation is equal to $2\pi$ radians.

Geostationary satellite

A satellite that orbits the Earth at a distance such that it completes one orbit every $24$ hours and appears stationary to an observer on the ground.

Tangential velocity

The velocity of an object moving along a circular path, which is proportional to the distance from the center of rotation and is always tangent to the motion.

Circumference

The linear distance around a circle, calculated as $2 \times \pi \times r$.

Rotational acceleration

The rate of change of rotational speed or direction.

Rotational inertia

A measure of how much an object resists changes to its rotational speed, determined by its mass and how that mass is distributed relative to the axis of rotation.

Torque

A twist or turn caused by a force that generates rotational acceleration, represented by the lowercase Greek letter tau $\tau$.

Newton-meters

The units used to measure torque.

Lever arm

The distance between the applied force and the center of rotation ($r$) used to maximize torque.

Mechanical equilibrium

An expanded state occurring when an object is traveling at a constant velocity and constant rotational speed, meaning the net force and net torque are both zero.

Positive torque

The sign given to a torque that causes an object to rotate counterclockwise.

Negative torque

The sign given to a torque that causes an object to rotate clockwise.

Center of mass

The average point of mass distribution in an object and the point around which it rotates.

Center of gravity

The point where the weight of an object is distributed; it is usually collocated with the center of mass unless the object is extremely tall, like the Burj Khalifa.

Stability

The measure of how easily an object will topple over, determined by whether the center of mass remains over the support base.

Angular momentum

The product of rotational inertia and rotational speed, which is conserved in the absence of an external torque.

Centripetal force

A center-seeking force that keeps an object moving in a circular path, calculated as $F_c = \frac{m \times v^2}{r}$.

Centripetal acceleration

The acceleration pointing toward the center of a circular path, calculated as $a_c = \frac{v^2}{r}$.