Glossary
Angular Acceleration (α)
The rate of change of angular velocity over time, indicating how quickly an object's rotational speed is increasing or decreasing.
Example:
When a car's engine revs up, its crankshaft undergoes significant angular acceleration.
Angular Impulse
The product of the average net torque and the time interval over which it acts, resulting in a change in angular momentum. It is the rotational equivalent of linear impulse.
Example:
A quick, strong push on a merry-go-round applies an angular impulse, causing it to spin faster.
Angular Momentum (L)
A measure of an object's rotational motion, analogous to linear momentum for translational motion. It quantifies how much an object is rotating and how difficult it is to stop that rotation.
Example:
A figure skater pulling their arms in to spin faster demonstrates the conservation of angular momentum.
Angular Velocity (ω)
The rate at which an object rotates or revolves relative to another point, measured in radians per second. It describes how fast something is spinning.
Example:
A record player spinning at 33 1/3 revolutions per minute has a specific angular velocity.
Clockwise Rotation (Negative)
A convention in physics where rotation in the clockwise direction is assigned a negative value for angular quantities like torque, angular velocity, and angular momentum.
Example:
If a car tire spins backward, its angular velocity would be described as clockwise rotation (negative).
Counterclockwise Rotation (Positive)
A convention in physics where rotation in the counterclockwise direction is assigned a positive value for angular quantities like torque, angular velocity, and angular momentum.
Example:
When looking down at a spinning top, if it rotates to the left, its angular velocity is considered counterclockwise rotation (positive).
External Interactions (Angular Momentum)
Forces or torques originating from outside a defined system that can cause a change in the system's total angular momentum.
Example:
A spinning ice skater pushing off the ice with their skate experiences external interactions that change their angular momentum.
Linear Momentum (p) (in context of angular momentum)
The product of an object's mass and its linear velocity, representing its translational motion. For an object moving in a straight line, it can contribute to angular momentum relative to a fixed point.
Example:
A comet flying past a planet has linear momentum, but it also possesses angular momentum relative to the planet's center.
Moment of Inertia (I)
A measure of an object's resistance to changes in its rotational motion, analogous to mass in linear motion. It depends on the object's mass distribution and the axis of rotation.
Example:
A tightrope walker uses a long pole to increase their moment of inertia, making it harder for them to rotate and fall.
Net Torque (τ_net)
The sum of all torques acting on a system, which causes a change in the system's angular momentum. It is the rotational equivalent of net force.
Example:
Applying a wrench to a stubborn bolt requires a significant net torque to get it to turn.
Torque (τ)
A twisting force that tends to cause rotation around an axis, calculated as the product of force and the perpendicular distance from the pivot point.
Example:
Pushing on a door handle far from the hinges creates more torque than pushing near the hinges, making the door easier to open.
Vector Quantities (Rotational)
Physical quantities in rotational motion (like torque, angular velocity, angular acceleration, and angular momentum) that possess both magnitude and direction.
Example:
Understanding the direction of the vector quantities like angular velocity is crucial for predicting which way a spinning top will precess.