# Active Physics Vocabulary List

## Measurement

accuracy
How close the measured value is to the standard or accepted value of that measurement.
SI system
A complete system of units of measurement for scientists; fundamental quantities are:
• length (meter)
• mass (kilogram)
• time (second)
• electric current (ampere)
• temperature (Kelvin)
• matter (mole)
• luminous intensity (candela)
Mass
A measure of how much material something contains. This shouldn't be confused with weight. SI unit is the kilogram (kg). 2.3
Volume
A measure of how much space an object occupies. Derived SI unit is meters3, commonly also cm3. For liquid measure liter or ml.
Meter
The standard unit of length in the SI system of measure that equals 39.37 inches. SI unit is the meter (m).
Centimeter
A unit of measure in the metric system of measurement equivalent to 1/100 of a meter or 0.3927 inch; abbreviated is cm.
Slope of graph
The mathematical result of the change in the y axis of a line divided by the corresponding change on the x axis.
Scalars
Scalars are quantities that are fully described by a magnitude (or numerical value) alone. Example: 25 mph
Vectors
Vectors are quantities that are fully described by both a magnitude and a direction. Example: 25 mph South

## Inquiry

Manipulated variable
Object or condition that you change on purpose to test your hypothesis.
Responding variable
Object or condition that changes when you change the manipulated variable in a scientific investigation.
Controlled variable
An object or condition you want to remain constant when you carry out a scientific investigation.
System
Group of interacting, interrelated, or interdependent parts made up of matter and energy that form a complex whole.
Subsystem
A major part of a system which itself has the characteristics of a system.
Thought experiment
An experiment that cannot be or is not carried out in practice; it is reasoned through by thought and intuition. 3.9

## Chapter 2 Motion

Acceleration
The rate at which an object's velocity changes with time. It involves a change in the speed (increase or decrease) OR direction OR both speed and direction. Basic SI unit is meters per second squared (m/s2).
Accel = Δ velocity / Δ time OR Δ direction.   2.2
Centripetal force
The force making a motion in a circle possible, always directed to the center of the circle. 2.4
Force
Push or pull that gives energy to an object, sometimes causing a change in the motion of the object. 2.1
Frame of reference
Any system for specifying the precise location of objects in space. 3.7
Friction
A force that resists motion between two objects in contact. 2.1
Inertia
The tendency of matter to remain at rest if at rest, or to remain in motion in a straight line if in motion. 2.1
Kgm/s2
The base units that make up a Newton (a unit of force). 2.5
Motion
A change in the position or location of one thing with respect to another. 2.1
Net force
Sum of all the forces acting on an object. 2.5
Newton's First Law (Law of Inertia)
If there is no net force on an object, then its velocity is constant. The object is either at rest (if its velocity is equal to zero), or it moves with constant speed in a single direction.
Newton's Second Law
The acceleration a of a body is parallel and directly proportional to the net force F acting on the body, is in the direction of the net force, and is inversely proportional to the mass m of the body, i.e., F = ma.
Newton's Third Law (Action/reaction force pairs)
When a first body exerts a force F1 on a second body, the second body simultaneously exerts a force F2 = – F1 on the first body. This means that F1 and F2 are equal in magnitude and opposite in direction.
Speed
Distance traveled per unit time. SI unit is meters/sec (m/s).
Speed = Δ distance / Δ time.   2.1
Unbalanced force
A force that is not countered by another force in the opposite direction. 2.5
Velocity
Rate of change of position OR direction of an object.
Velocity = Δ distance / Δ time OR Δ direction.   2.4
Weight
The force of gravity acting on a body, equal to the mass of the body multiplied by the acceleration of gravity. 2.3

## Energy

Energy
Energy is the ability a system has to produce changes on another system.
Heat
The transfer of energy from one object at a higher temperature to another object at a lower temperature.
Kinetic energy
The energy possessed by a moving object. = ½ mv2.
Momentum
Mass times velocity; a quantity that determines the potential force that an object can impart to another object by collision.
Potential energy
Stored energy of a material, a result of its position in an electric, magnetic, or gravitational field. PE=mgh.
Thermal energy
Energy in the form of heat - the total internal kinetic and potential energy of an object due to the random motion of its atoms and molecules.
Work
The transfer of energy from one object or system to another by applying a force over a distance. The formula is (force) x (distance).

## Chapter 3 Waves

Amplitude
The height of the wave. In sound waves referred to as 'volume'. 3.5
Constructive interference
When waves align and the resulting wave has troughs and crests that are larger. 3.6
Crest
The highest part of a wave. The curved tops or ridges of an oscillating wave. 3.5
Destructive interference
When waves align and the resulting wave has troughs and crests that are smaller. 3.6
Electromagnetic waves
Radiation consisting of waves of energy sent through space and matter associated with electric and magnetic fields resulting from the acceleration of an electric charge (light, x-rays, microwaves, gamma rays, etc.). 3.9
Frequency
The number of back-and-forth cycles per second, in a wave or wave-like process. In sound waves referred to as pitch. 3.5
Gravitational field
An attraction field created by any object with mass, extending outward in all directions, which determines the influence of that object on all others. 3.2
Longitudinal waves
A wave in which the individual particles of a medium vibrate back and forth in the direction in which the wave travels. See Sound. 3.5
Mechanical waves
Waves which travel through a medium - sound waves, water waves and waves in solid objects.
Period
The time for one wavelength to pass a point. The time for a wave to travel the distance of one wavelength. T = 1/frequency. 3.5
Photovoltaic cell
An electronic device consisting of layers of semiconductor materials that is capable of converting light directly into electricity. 3.2
Primary waves
P waves, or compression waves, are seismic body waves that shakes the ground back and forth in the same direction as the direction the wave is moving.
Reflection
The change in direction (or return) of waves striking a surface. (3.6)
Refraction
Waves change direction as they pass from one medium to another.
Secondary waves
S waves, are seismic body waves that shakes the ground back and forth perpendicular to the direction the waves are moving.
Sound
Mechanical energy vibrations transmitted as waves through a solid, liquid, or a gas that can be detected by the human ear. 3.5
Speed
The velocity of a traveling wave (distance traveled per time). 3.6
Superposition
The addition of two or more waves to produce a new wave. (3.6)
Transverse waves
A wave in which the vibrations of the medium are perpendicular to the direction the wave is moving. 3.5
Trough
The lowest part of a wave, between successive crests. 3.5
Wave
A rhythmic disturbance that transfers energy from place to place. 3.5
Wave interference
The superposition (overlapping) of two or more waves resulting in a new wave pattern. 3.6
Wavelength
The distance measured from crest to crest of one complete wave or cycle. 3.5
Wave medium
The material that can carry a mechanical wave.