Rotational kinetic energy

The energy of a particle rotating around an axis.

Rotational motion

Occurs when every point in the rigid body moves in a circular path around a line called the axis of rotation.

Second Law of Thermodynamics

There are a few versions of this law. One is that heat flows spontaneously from hot to cold, but not in the reverse direction. Another is that there is no such thing as a 100% efficient heat engine. A third states that the entropy, or disorder, of a system may increase but will never decrease spontaneously.

Sound

Waves carried by variations in air pressure. The speed of sound waves in air at room temperature and pressure is roughly 343 m/s.

Specific heat

The amount of heat of a material required to raise the temperature of either one kilogram or one gram of that material by one degree Celsius. Different units may be used depending on whether specific heat is measured in s of grams or kilograms, and joules or calories.

Speed

A scalar quantity that tells us how fast an object is moving. It measures the rate of change in distance over time. Speed is to be contrasted with velocity in that there is no direction associated with speed.

Spring

Objects that experience oscillatory or simple harmonic motion when distorted. Their motion is described by Hooke’s Law.

Spring constant

Indicates how “bouncy” or “stiff” a spring is. More specifically, the spring constant, k, is the constant of proportionality between the restoring force exerted by the spring, and the spring’s displacement from equilibrium. The greater the value of k, more resistant the spring is to being displaced.

Static friction

The force between two surfaces that are not moving relative to one another. The force of static friction is parallel to the plane of contact between the two objects and resists the force pushing or pulling on the object.

Superposition

The principle by which the displacements from different waves traveling in the same medium add up. Superposition is the basis for interference.

System

A body or set of bodies that we choose to analyze as a group.

Tail

In the graphical representation of vectors, the tail of the arrow is the blunt end (the end without a point).

Temperature

A measure of the average kinetic energy of the molecules in a system. Temperature is related to heat by the specific heat of a given substance.

Tension force

The force transmitted along a rope or cable.

Third Law of Thermodynamics

An object cannot be cooled to absolute zero.

Torque

The effect of force on rotational motion.

Uniform circular motion

The motion of a body in a circular path with constant speed.

Unit vector

A unit vector is a vector with length 1.

Vector

A vector quantity, or vector, is an object possessing, and fully described by, a magnitude and a direction. Graphically a vector is depicted as an arrow with its magnitude given by the length of the arrow and its direction given by where the arrow is pointing.

Velocity

A vector quantity defined as the rate of change of the displacement vector with time. It is to be contrasted with speed, which is a scalar quantity for which no direction is specified.

Wave

A system with many parts in periodic, or repetitive, motion. The oscillations in one part cause vibrations in nearby parts.

Wave speed

The speed at which a wave crest or trough propagates. Note that this is not the speed at which the actual medium (like the stretched string or the air particles) moves.

Wavelength

The distance between successive wave crests, or troughs. Wavelength is measured in meters and is related to frequency and wave speed by = v/f.

The unit of magnetic flux, equal to one T · m².

Weight

The gravitational force exerted on a given mass.

Weightlessness

The experience of being in free fall. If you are in a satellite, elevator, or other free-falling object, then you have a weight of zero Newtons relative to that object.

Work

Done when energy is transferred by a force. The work done by a force F in displacing an object by s is W = F · s.

Work function

The amount of energy that metal must absorb before it can release a photoelectron from the metal.

Work-energy theorem

States that the net work done on an object is equal to the object’s change in kinetic energy.

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