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# Physics 2nd quarter

### Vocabulary for the second half of Physics

Term | Definition |
---|---|

Rotational Motion | Movement in a circle or spinning units; degrees, revolutions, radians |

Radian | Angle formed when an arc length is equal to the radius of a circle. |

Angular Displacement | delta theta rotational counterpart to delta x. |

Angular speed | Rate at which an object moves through an angle. Rotational counterpart to linear velocity abbreviation: omega SI Unit: rad/sec |

Angular Acceleration | Rate of change in angular speed. rotational counterpart to linear acceleration Abbreviation:lower-case alpha SI Unit: rad/sec^2 |

Centripetal Acceleration | Acceleration Toward the center of a circle Abbreviation: a sub c SI Unit: m/sec^2 |

Centripetal Force | Net force acting toward the center of a circle keeping an object moving in a circular direction. Abbreviation: F sub c SI Unit: N |

Centrifugal Force | Imaginary outward force felt by observers moving in a circular path. Abbreviation: F sub g SI Unit: N |

Kepler's 1st Law | Each Planet travels in an elliptical orbit around the sun with the sum at one of the focal points. |

Kepler's 2nd Law | An imaginary line drawn from the sun to any planet sweeps out equal areas in equal time intervals. |

Kepler's 3rd Law | The square of a planet's orbital period (T) is proportional to the cube of the average distance (r^3) between the planet and the sun. |

Center of Gravity | A point from which the weight of a body or system may be considered to act. (In uniform gravity it is the same as the center of mass.) |

Torque | Quantity that measures the ability of a force to rotate an object about some axis. Rotational counterpart to linear force SI Unit: Nm or Kg(m/s)^2 Max torque at 90 degrees, no torque at 0 or 180 degrees |

Rotational Equilibrium | When net torque and net force is zero. (Means that something is spinning at a constant speed) |

Inertia | The tendency of an object to resist a change in momentum. |

Moment of Intertia | The tendency of an object to resist a change in rotational motion. Abbreviation: I SI Unit: Kg*m^2 |

Moment of Inertia for a hoop | mr^2 |

Moment of Inertia for a cylinder/solid disk | (mr^2)/2 |

Mass Density | Concentration of matter in an object Abbreviation: Latin letter rho SI Unit: Kg/(m^3) |

Buoyant Force | Upward force exerted by a fluid on an object immersed in or floating on the fluid. Abbreviation: F sub b SI Unit: N |

Archimedes' Principle | An object completely or partially submerged in a fluid experiences an upward buoyant force equal in magnitude to the weight of the fluid displaced by the object. |

Pressure | Magnitude of the force on a surface per unit area Abbreviation: P Equation: P=F/A SI Unit: N/(m^2) or Pascal (Pa) |

Barometer | Devise used for measuring air pressure. |

Pascal's Principle | Pressure applied to a fluid in a closed container is transmitted equally to every point of the fluid and to the walls of the container. |

Ideal Liquid | A liquid with no internal friction, it is non=viscus. Steady and non-turbulent flow. |

Principle of Fluid Flow | The mass of the fluid flowing into a pipe must equal the mass of fluid flowing out of the pipe. |

Venturi Effect | The speed of a fluid increases when the cross sectional area decreases. |

Flow Rate | The product of A*v for a pipe. Flow rate is constant. Units: (m^3)/sec or CFM |

Bernoulli's Principle | The pressure in a fluid decreases as the velocity of the fluid increases. |

Magnus Force | A force created by Bernoulli's principle. "lift." |

Temperature | Measure of the average kinetic energy of particles in a substance. Abbreviation: T SI Unit: Kelvin (K) |

Internal Energy | The energy of a substance due to both the random motion of its particles and to the potential energy that results from the distances and alignments between particles. |

Thermal Equilibrium | The state in which two bodies in physical contact with one another have identical temperatures. |

Thermal Expansion | Generally, as temperature rises, so does volume. |

Coefficient of Volume Expansion | Quantity that relates the change in volume of an object to change of temperature. |

Heat | Energy transferred between objects due to a difference in temperature. Abbreviation: Q SI Unit: J (Joules) |

Conduction | Heat transferred due to direct contact. |

Convection | Heat transferred by the mixing of matter. (Happens with magma) |

Radiation | Heat transferred through electromagnetic waves. |

Thermal Insulators | Slowly transfer energy as heat (Slow due to pockets of trapped air). |

James Prescott Joule | Designed a device to show that energy transferred due to work can be turned into internal energy. |

Specific Heat Capacity | Quantity of heat required to raise a unit mass of homogeneous material 1k or 1 degrees C in a specified way given constant pressure and volume. Abbreviation: C sub p SI Unit: J/Kg(k) or J/kg(C) |

Calorimetry: | An experimental procedure used to measure the energy transferred from one substance to another as heat. |

Phase Change | Physical change in a substance from one state of matter to another at constant temperature and pressure. |

Latent Heat | The energy per unit mass that is transferred during a phase change of a substance. Abbreviation: L SI Unit: J/kg |

Latent Heat Fusion | L sub f Needed to melt 1 kg |

Latent Heat Vaporization | L sub v Needed to boil 1 kg |

Simple Harmonic Motion | Vibration about an equilibrium position in which a restoring force is proportional to the displacement from equilibrium. |

Restoring Force | The force towards the equilibrium point. Abbreviation: F |

Hooke's Law | The restoring force of a spring depends on the stiffness of the spring and the displacement from the spring's equilibrium point. |

Amplitude | The maximum displacement from the equilibrium point. Abbreviation: A SI Unit: m |

Period | The time it takes a complete cycle to occur. Abbreviation: T SI Unit: s (seconds) |

Frequency | The number of cycles or vibrations per unit of time. Abbreviation: f SI Unit: Hertz (Hz) or 1/sec |

Simple Pendulum | For small angles (less than 15 degrees), the motion of a pendulum is SHM. This is because for small angles Sin(x) is about x in radians. Gravity is the restoring force. |

Wave | Undulation or disturbance that transfers energy. (Energy, not matter, is transferred). |

Medium | Physical environment through which a disturbance can travel. |

Mechanical Wave | A wave that requires a medium through which to travel. (ie, water waves, rope waves, etc.) |

Pulse Wave | A wave consisting of a single traveling pulse. |

Periodic Wave | Wave formed by the period or motion of a wave source. |

Transverse wave | Wave whose particles vibrate perpendicularly to the direction the wave is traveling. |

Wavelength | Length from crest to crest, trough to trough, etc. Abbreviation: upside-down y SI Unit: m |

Longitudinal Wave | Wave whose particles vibrate parallel to the direction the wave is traveling. (ie, compression wave, density wave, pressure wave, etc). |

Compression | Area where a longitudinal wave is compressed. |

Rarefaction | Where the density and pressure are at a minimum in a longitudinal wave. |

Superposition | The combination of two overlapping waves (interference). |

Constructive Interference | Two or more ways in which individual displacements of the same side of the equilibrium position are added together to form a resultant wave. |

Destructive Interference | Trough and crest cancel each other out. (Utilized by noise-cancelling headphones). |

Free Boundary Reflection | The medium moves perpendicular to the wave. (The medium is not fixed in place). |

Fixed Boundary Reflection | The medium is fixed in place, so crests bounce back as troughs, and vice versa. |

Standing Wave | A wave pattern that results when two waves of equal frequency, wavelength, and amplitude travel in opposite directions and interfere. |

Node | Zero displacement in a standing wave. |

Antinode | Largest displacement in a standing wave. |

Sound Waves | Compression waves produced by vibrating objects. |

Ultrasonic Waves | A frequency above 20,000 Hz. |

Infrasonic Waves | A frequency below 20 Hz. |

Pitch | A measure of how high or low a sound is perceived to be; depends on the frequency. |

Subsonic | Slower than the speed of sound. |

Supersonic | Faster than the speed of sound. |

Sonic Boom | When an object passes the speed of sound, this occurs. |

Mach Number | Multiple of the speed of sound for a moving object. (Mach 1 is the speed of sound, Mach 2 is 2x the speed of sound) |

Doppler Effect | An observed change in frequency when there is relative motion between the source of waves and an observer. |

Sound Intensity | The rate at which energy flows through a unit area perpendicular to the direction of the wave motion. Abbreviation: I SI Unit: W/(m^2) W=watts |

Decibel (dB) | A dimensionless unit that describes the ratio of two intensities of sound; the threshold of hearing is commonly used as the reference intensity. |

Forced Vibration | When objects are connected, vibrations in one object will be transferred to others, causing them to vibrate. Vibrations from one object that strikes another. |

Sympathetic Vibrations | Vibrations that occur because of other vibrating objects. |

Natural Frequency | The frequency at which an object will vibrate when set in motion. |

Resonance | A phenomenon that occurs when the frequency of a force applied to a system matches the natural frequency of vibration of the system, resulting in a large amplitude of vibration. |

Fundamental Frequency | The lowest frequency of vibration for a standing wave. |

Harmonics | Integral multiples of the fundamental frequency (overtones). |

Harmonic series | A series of frequencies that includes the fundamental frequency and successive harmonics |

Timbre | The musical quality of a tone resulting from the combination of harmonics present at different intensities (sound quality). |

Reverberation Time | The amount of time it takes for the intensity of a sound echo to decrease by 60 dB. |

Anechoic Chamber | A room that provides virtually no echoes. |

Beats | The periodic variation in the amplitude of a wave that is the superposition of two waves of slightly different frequencies. |

White Light | Combination of electromagnetic frequencies. |

Electromagnetic Wave | A wave that consists of oscillating electric and magnetic fields, which radiate outward from the source at the speed of light. |

Luminous Flux | Rate at which light is emitted from a source (brightness). Measured in lumens. |

Illuminance | luminous flux divided by surface area. SI Unit: lm/m^2 or lux |

Reflection | The change in direction of an electromagnetic wave at a surface that causes it to move away from the surface. |

Virtual Image | An image from which light rays appear to diverge, even though they are not actually focused there; a virtual image is not able to be projected onto a screen. |

Concave Spherical Mirror | A mirror whose reflecting surface is a segment of the inside of a sphere. |

Real Image | An image that is formed by the intersection of light rays (can be projected onto a screen). |

Paraxial Rays | Light rays that are very near the principal axis of the mirror and are used in ray diagrams. Rays farther from the axis don't necessarily intersect after reflecting from a concave mirror (spherical aberrations). |

Convex Spherical Mirror | A mirror whose reflecting surface is an outward-curved segment of a sphere. |