Mechanics vocab - simple pendulum

Velocity (v)

Vector quantity of speed and direction of an object.

Relative motion (velocity)

Comparison of two or more objects' motions, assuming that the second object is fixed by looking at the reference frame of the second object.

Trajectory

The path of an object in projectile motion.

Kinetic friction (force)

Opposes sliding motion, constant.

Static friction (force)

Prevents motion.

Normal force (N)

Support force exerted by a surface perpendicular to the surface itself.

Tension (T)

Pulling force transmitted through a string, rope or cable when stretched, equal throughout.

Elastic force

Restoring force exerted by an object when it is deformed.

Buoyant force (N)

Upward force exerted by a fluid on a submerged object.

Archimedes' principle

The buoyant force exerted on a submerged object is equal to the weight of the displaced fluid.

Transactional equilibrium

Sum of all forces in any direction is zero.

Rotational equilibrium

Sum of all torques about any pivot point is zero.

Torque (τ)

Rotational effect of a force applied at a distance from a pivot point.

Couple of forces

A pair of equal and opposite forces acting on a body but not along the same line, causing torque but no rotation.

Center of mass

Point where the entire mass of an object or system can be considered to be concentrated for motion analysis.

Newton's I law

If an object is not interacting with other objects (affected by forces) it remains at rest or continues to move in a straight line with constant speed.

Newton's II law

The net force acting on an object gives it an acceleration proportional to the force.

Newton's III law

When two objects interact, they exert forces on each other that are equal in magnitude but opposite in direction.

Rolling resistance

Force that opposes the motion of a rolling object due to deformation, internal friction and surface interaction.

Air resistance

Drag force that opposes the motion of an object moving through air.

Terminal velocity

Maximum speed attainable by an object falling through a fluid or gas.

Coefficient of restitution (e)

Measurement of how 'bouncy' a collision is between two objects.

Principle of work and kinetic energy

Work done by the sum of all forces acting on a particle is equal to the change in the kinetic energy of the particle.

Impulse (J)

Change in momentum caused by a force acting over a specific time interval.

Impulse-momentum theorem

Impulse is equal to the change in momentum.

Fission

Process where a single object splits into two or more parts, conserving total momentum.

Coalescence

Two or more objects combining to form a single object, conserving total momentum.

Elastic collision

Both momentum and kinetic energy are conserved; coefficient of restitution is 1.

Inelastic collision

Momentum is conserved, but kinetic energy is not; 0 < e < 1.

Perfectly inelastic collision

Objects stick together after the collision; momentum is conserved and e = 0.

Uniform circular motion

An object moves in a circular path at constant speed.

Linear velocity (v)

Speed of an object on its circular path.

Angular velocity (ω)

Circular motion speed in rad/s.

Period (T)

Time to complete one full revolution (2π).

Rotational frequency (f)

Number of revolutions per second, measured in Hz.

Centripetal force

Force that causes circular motion, directed towards the center of the circular path.

Non-uniform circular motion

Involves changing speed; includes centripetal and tangential acceleration.

Inertial force

Force that appears when looking at an accelerating force in a rotating reference frame.

Centrifugal force

Inertial force acting away from the center of rotation in a rotating frame.

Inertia

Resistance to a change in motion.

Simple harmonic motion

Periodic motion similar to uniform circular motion, such as a mass on a spring.

Restoring Force

The force that pulls the object back toward equilibrium.

Amplitude (A)

The maximum displacement from equilibrium in harmonic motion.

Period (T)

The time for one full oscillation.

Frequency (f)

How many oscillations occur per second.

Phase (ϕ)

Determines the starting position of the motion.

Angular Frequency (ω)

A measure of how fast the system oscillates in radians per second.

Simple pendulum

A mass attached to a rod pivoted at its other end.