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 meters^{3}, commonly also cm^{3}. 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/s^{2}).
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/s^{2}
 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 F_{1} on a second body, the second body simultaneously exerts a force F_{2} = – F_{1} on the first body. This means that F_{1} and F_{2} 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 mv^{2}.
 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, xrays, microwaves, gamma rays, etc.). 3.9
 Frequency
 The number of backandforth cycles per second, in a wave or wavelike 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.