Mechanics

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Displacement
The distance in a given direction from a fixed origin. It is a vector.
Velocity
The rate of change with time of the displacement vector. It is a vector. It is the gradient of a graph of displacement versus time.
Speed
The rate of change with time of distance. It is scalar.
Acceleration
The rate of change with time of the velocity vector. It is a vector. Its magnitude is given by the gradient of a graph of velocity versus time.
Newton's First Law of Motion
If the net external force on a system is zero, the system remains at rest or moves with constant velocity.
Newton's Second Law of Motion
The net force on a body equals the rate of change of the body's momentum.
Newton's Third Law of Motion
If body A exerts a force on body B, then body B will exert an equal and opposite force on body A.
Translation equilibrium
The state of a system where the net external force is zero.
Momentum
If the net external force on a system is zero, the total momentum of the system stays the same.
Impulse
The total change in the momentum of a system as a result of a force acting on it. Its magnitude is given by the area under a force versus time graph. It is a vector.
Work
The product of the force times the distance moved by its point of application in the direction of the force. It is given by the area under the graph of force versus distance. It is a scalar.
Power
The rate at which work is being performed. It is a scalar.
Efficiency
The ratio of useful output work (or power) to input work (or power).
Centripetal force
The name of any force or resultant of individual forces that points toward the center of a circular path.
Gravitational field strength
The gravitational force experienced by a point test particle of unit mass. It is a vector.
Gravitational potential
The work done in bringing a point test particle of unit mass from infinity to a point in a gravitational field. It is a scalar.