Glossary
Acceleration
The rate at which an object's velocity changes. This can involve speeding up, slowing down, or changing direction.
Example:
When a roller coaster speeds up as it plunges down a hill, it experiences significant positive acceleration.
Average Acceleration
The total change in an object's velocity divided by the total time taken for that change. It describes the overall rate of velocity change.
Example:
A car that goes from 0 to 20 m/s in 5 seconds has an average acceleration of 4 m/s².
Average Velocity
The total displacement of an object divided by the total time taken for that displacement. It represents the overall rate of position change.
Example:
If a runner covers 100 meters in 10 seconds, their average velocity is 10 m/s in the direction of their run.
COM Acceleration
The acceleration of the center of mass of a system, determined by the net external force acting on the system divided by its total mass.
Example:
If a rocket expels gas, the COM acceleration of the rocket-gas system remains constant if no external forces act on it.
COM Velocity
The velocity of the center of mass of a system, representing the overall translational motion of the entire system.
Example:
When a diver performs a flip, their body rotates, but their COM velocity follows a parabolic trajectory.
Center of Mass (COM)
The unique point where the weighted average of all the masses in a system is located. It is the point where the system would balance if supported.
Example:
For a perfectly symmetrical object like a baseball, the center of mass is at its geometric center.
Centripetal Acceleration
The acceleration experienced by an object in uniform circular motion, always directed towards the center of the circular path. It is caused by the change in direction of the velocity vector.
Example:
When a car takes a sharp turn, the passengers feel pushed outwards, but the car itself is experiencing centripetal acceleration towards the center of the turn.
Centripetal Force
The net force required to keep an object moving in a circular path, always directed towards the center of the circle. It is not a new type of force but rather the net force provided by other forces like tension or friction.
Example:
The tension in a string keeping a ball swinging in a circle is the centripetal force.
Displacement
The change in an object's position, measured as a straight-line distance and direction from the initial to the final point. It is a vector quantity.
Example:
Walking 10 meters east and then 10 meters west results in a zero displacement, even though you walked 20 meters.
Non-Uniform Motion
Motion where an object's velocity is changing, implying that the object is accelerating.
Example:
A car navigating city traffic, constantly speeding up, slowing down, and turning, exhibits non-uniform motion.
Position
The location of an object in space, often described by coordinates relative to an origin.
Example:
If you're at the 5-meter mark on a track, your position is 5m from the starting line.
SUVAT Equations
A set of kinematic equations used to describe motion with constant acceleration, relating displacement (S), initial velocity (U), final velocity (V), acceleration (A), and time (T).
Example:
To find how far a dropped ball falls in a certain time, you would use the SUVAT equations.
Uniform Circular Motion (UCM)
The motion of an object moving in a circular path at a constant speed. Although speed is constant, velocity changes due to continuous change in direction.
Example:
A satellite orbiting Earth at a steady altitude and speed is undergoing Uniform Circular Motion.
Uniform Motion
Motion characterized by constant velocity, meaning the object moves in a straight line at a steady speed with zero acceleration.
Example:
A train moving at a steady 50 km/h on a straight track is an example of uniform motion.
Velocity
The rate at which an object's position changes, including both its speed and direction. It is a vector quantity.
Example:
A car traveling at 60 mph north has a different velocity than a car traveling at 60 mph south.