Physics Flashcards
Scalar
a physical quantity that has a magnitude but no direction
Vector
a physical quantity with both magnitude and direction
Instantaneous speed/velocity
speed/velocity at any one point in time
Acceleration
the rate of change in velocity
Positive slope displacement vs time
object is moving toward the positive direction
Negative slop displacement vs time
object is moving toward the negative direction
Flat slope displacement vs time
object is at rest
Positive slope velocity vs time
object is accelerating in the positive direction
Negative slope velocity vs time
object is accelerating in the negative direction
Flat slope velocity vs time
object maintains a constant velocity
Area velocity vs time
distance/displacement the object has traveled
Flat slope acceleration vs time
constant/uniform acceleration
Area acceleration vs time
change in velocity of an object
Mass
quantitative measure of an object’s inertia; tells us how much that object will resist a change in motion
Weight
gravitational force that an object experiences when it it close to a much larger body
Center of mass
the single point at which all of the system’s mass can be considered to be concentrated; if a force is applied to an object beyond its center of mass, the object will rotate
Newton’s first law of motion
the law of inertia, an object in a state of rest or motion will tend to remain that state unless it is acted upon by a net force
Newton’s second law of motion
when a net force acts on an object, the change in that object’s state of motion will be inversely proportional to the mass of the object and directly proportional to the net force
Newton’s third law of motion
for every action, there exists an equal and opposite reaction
Normal force
always perpendicular to the force that applies it
Friction
force that opposes slipping/relative motion that is caused by attractive molecular forces between surfaces that are in contact
Static friction
occurs when a contact force is applied to an object and the surfaces do not slide past one another; object is not in motion relative to its surface; increases proportionally with the magnitude of the contact force until the object begins moving
Kinetic friction
friction experience when object begins moving and remains constant in magnitude, weaker than static friction
Air resistance
results from an object’s collisions with air molecules which impede relative motion between the object and the air; dependent on surface air, velocity of object, and shape
Hooke’s law
descries the force that most objects apply against a deforming force
Yield point
the point of violation in which solids do not follow Hooke’s law; when an object is deformed beyond its yield point it loses the ability to regain its original shape
Fracture point
the objects breaks (hooke’s law)
Torque
the measure of a force’s ability to cause rotational acceleration
Equilibrium
a state in which there is no net force and no net torque
Static equiibrium
equilibrium when all velocities are zero
Dynamic equiliobrum
equilibrium when velocities are nonzero but all velocities are constant
Mechanical energy
energy of a macroscopic system ie. kinetic and potential energy
Kinetic energy
energy of motion
Potential energy
energy of position
Gravitational potential energy
potential energy created by the force of gravity
Elastic potential energy
when a restorative elastic force acts on an object
Work
energy transferred for any reason other than a temperature difference
Heat
energy that is transferred between a system and its surroundings due to a temperature difference between them
First Law of Thermodynamics
any change in the total energy of a system is due to work or heat
Work-Kinetic Energy Theorem
work is equal to the change in kinetic energy in the absence of heat and change in potential energy
Sign conventions for work
work by the system (-); work on the system (+)
Power
rate of energy transfer
Law of Conservation of Mechanical Energy
when only conservative forces are acting, the sum of mechanical energies remains sconstant
Conservative forces
have associated potential energy and system experiences no change in total mechanical energy ie. gravitational forces and Hooke’s law forces
Non-conservative forces
the mechanical energy of the system changes ie. friction
Machine
reduces the force required to do a given amount of work but does not change work
Mechanical advantage
the ability to reduce applied force
Ramp
an inclined plane that reduces the force needed to do work by increasing the distance over which the force is applied
Lever
a beam attached to a fulcrum and reduces the force needed to do a given amount of work by increasing the distance over which the force is applied
Non-ideal machine
a system in which some of the energy transferred as work done on the machine is lost to friction ,deformation etc. so more work is required than would be in the absence of the machine (force is still reduced)
Fluid
liquid or gas; molecular bonds are constantly breaking and reforming due to the high kinetic energy of the molecules
Density
heaviness of a fluid; mass/volume
Specific gravity
the ratio of the density of an object to the density of water
Density of water
1000 kg/m3 or 1 g/cm3
Fluid pressure
pressure experienced by the object as a result of the impulse of molecular collisions
Atmospheric pressure
101,000 Pa
Pascal’s principle
states that pressure applied anywhere to an enclosed incompressible fluid will be distributed undiminished throughout the fluid
Absolute pressure
pressure of a system relative to a vacuum
Gauge pressure
amount by which a system’s pressure deviates from atmospheric pressure
Hydraulic lift
simple machine that works via Pascal’s principle; piston 1 has a much smaller area than piston 2; both pistons must exert the same pressure at the point of contact with the liquid; the ratio of force to area will stay the same for piston 2 so with a large area, it will be subject to an even greater force
Buoyant force
a standing fluid force which results from a pressure difference between the top of an object and the bottom of it
Floating object
density of object is less than density of fluid; displaces a volume of fluid with mass equal to its own mass; Fb = Fg
Submerged object
density of object is equal to the density of the fluid; displaces volume fluid with mass equal to its own mass and equal to its own volume; Fb = Fg
Sunk object
density of object greater than density of fluid; displaces volume of fluid equal to its own volume; Fb < Fg
Random translational motion
contributes to fluid pressure as in a fluid at rest
Uniform translational motion
shared equally by all the molecules at a given location in a fluid
Characteristics of ideal fluid
no viscosity, incompressible/uniform density, no turbulence, irrotational flow
Viscosity
a measure of a fluid’s temporal resistance to forces that are not perpendicular to its surface
Turbulence
the velocity at any fixed point in the fluid may vary with time
Laminar flow
all fluid flowing through any fixed point has the same velocity
Irrotational flow
any object moving with an ideal fluid will not rotate about its axis as it flows but will continue to point in one direction regardless of the direction of flow
Continuity equation
Q =Av
Streamlines
velocity of a party is tangent to its curve; magnitude of velocity is inversely related to the distance between streamlines
Bernoulli’s equation
restates conservation of energy in terms of densities and pressures; the sum o f the pressure, kinetic energy per unit volume, and potential energy per unit volume of a fluid remains constant throughout that fluid
Pitot tube
horizontal tube that contains a U-shaped tube which provides pressure measurements of the velocity of a fluid flowing past it
Venturi tube
horizontal tube with a constricted region in the middle.; provides measurements that can be used to calculate the velocity of a fluid flowing within it
Venturi effect
the decrease in pressure that occurs when a fluid flows into a constricted region of a pipe
Surface tension
describes the intensity of the intermolecular forces per unit length
Capillary action
a fluid is pulled up a thin tube due to adhesive forces
Adhesive force
forces between the molecules of the tube and the fluid molecules; if adhesive forces are stronger than cohesive, the fluid is pulled upward by the vertical component of the surface tension and a concave surface is formed
Cohesive forces
forces between the fluid molecules of a tube; if cohesive forces are stronger, a convex surface is formed as the fluid is pulled downward by the vertical component of surface tension
Field
some type of distortion or condition in space that creates a force on a charge
Lines of force
point in the direction of the field (positive to negative for electric fields)
Electric field
defined as the electrostatic force per unit charge (N/C or V/m)
Voltage
the potential for work by an electric field in moving any charge from one point to another; units of volts (J/C)
Equipotential surfaces
all points on an equipotential surface are at the same voltage
Conductors
allow electrons to flow relatively freely
Resistors
hold electrons tightly in place
Metallic conductors
conduct a charge through the transfer of electrons and no chemical change occurs as the result of that flow
Electrolytic conductor
characterized by a flow of ions in a membrane which entails a transfer of matter
Current
moving charge (A or C/s)
Drift speed
uniform translational movement
Circuit
cyclical pathway for moving charge where a battery provides the potential difference needed to maintain charge flow
Resistance
the quantitative measure of an object of a particular shape and size to resist the flow of charge (measured in ohms); increases with length and temperature
Electromotive force (EMF)
fancy word for voltage
Capacitor
temporarily stores energy in a circuit in the form of separated charge ; capacitance increases as plates’ surface area increases
Parallel plate capacitor
2 plates made from conductive material are separated by a very small distance
Dielectric constant
refers to the substance between the plates of a capacitor; acts to resist the creation of an electric field, allowing the capacitor to store more energy (constant of air = 1)
Dielectric strength
at some maximum voltage, the dielectric will break down and conduct electricity
Ammeter
instrument that measures the current flowing through a circuit; connected in series with a circuit so that all current flowing through the circuit also flows through the meter; the resistance within the ammeter is almost zero so it does not affect the current through the circuit
Voltmeter
instrument that measures the potential difference between any 2 points on a circuit; attached to 2 separate points on a circuit, often on either side of a circuit element; always attached in parallel so it does not affect the voltage of the circuit and should not draw current so the resistance if functionally infinite within a voltmeter
Multimeter
can serve as both an ammeter and a voltmeter; a switch determines whether current or voltage is measured
Production of sound
occurs via the vibration of a source such as the vocal chords
Wave
the propagation of some vibration from one point to another
Mechanical waves
obey the laws of classical mechanics and require a medium through which to travel ie. sound or waves on a string
Electromagnetic waves
do not require a medium through which to travel; they can propagate in vacuo or in a vacuum ie. light
Transverse wave
medium is displaced perpendicularly to the direction of wave propogation
Longitudinal wave
one in which the medium is displaced parallel to the direction of wave propagation
Nondispersive wave
wave maintains its shape and does not disperse as it travels
Wavelength
the distance from any point in the wave to the point where the wave begins to repeat itself
Frequency
the number of wavelengths that pass a fixed point in one second
Period
the time it takes the wave to travel the distance of one wavelength
Characteristics of medium that determine velocity of a wave
elasticity (resistance to change in shape) and inertia (resistance to change in motion)
Amplitude of a wave
the distance between the x-axis and either the top of a crest or bottom of a trough
Constructive interference
when the superposition of waves results in a greater displacement
Destructive interference
when the superposition of waves results in lesser displacement
Sound
transfer of energy through oscillations between high and low pressure
Pitch
a measure of how high or how low a note sounds
Intensity level
measure of loudness; describes how intense a sound seems to be
Relationship between intensity and decibel
if the intensity is increased by a factor of 10, the decibels increase by the addition of 10 decibels
Wave pulse
single wavelength
Resonance
the condition where the natural frequency and the driving frequency are equal
Attenuation (damping)
the decrease in the intensity of a wave propagating through a medium; due to reflection, spreading, absorption
Doppler effects
when the source or observer is moving toward the other, the observed frequency is higher than the source frequency; when the source or observer is moving away from each other, the observed frequency is lower than the source frequency
Beats
occur when 2 waves with slightly different frequencies are superimposed; at some points they will be nearly in phase and other points they will be out of phase
Shock wave
a conical wave front produced when the velocity of the sound source exceeds the velocity of the sound wave ; when the source moves faster than the speed of sound, many wave fronts overlap generating a region of very low pressure, air moves in response to this gradient creating a loud sonic boom
Mach number
the ratio of the velocity of the source to the velocity of the wave
Light
transfer of energy through alternating electric and magnetic fields
Photons
pulses of electromagnetic radiation that can be thought of as localized particles of energy
Absorption
the waves most likely to be absorbed are those whose frequencies most likely match the resonant frequencies of the medium
Polarized light
light with its electric and magnetic fields oriented in a particular, rather than random, way
Circularly polarized light
consists of electric fields of constant magnitude that change direction in a rotary manner in a clockwise or counterclockwise manner
Reflection
at the boundary between media, a wave bounces back and returns into the medium from which it came
Refraction
a wave bends as it continues from one medium to the next
Angle of incidence
the angle at which a wave strikes an interface
Angle of reflection
angle at which a wave reflects
Plane surface reflection
angle of incidence is equal to angle of reflection
Index of refraction
the ratio of the speed of light in a vacuum to the speed of light in a particular medium; air =1; water = 1.3; glass = 1.5
Total internal reflection
when light is coming from a medium with a higher index of refraction, the angle of incidence can be so great that all photons will be reflected and none will refract (this angle is called the critical angle)
Dispersion
the separation of light into different frequencies due to their different indices of refraction in a medium
Chromatic dispersion
white light (which is made up of all light frequencies in the visible spectrum) is split by a prism
Thin film interference
occurs when a thin layer of a substance is placed between 2 layers of another substance that has a different index of refraction; at each interface light can either reflect or refract; if it refracts, it changes wavelengths but not phase; if it reflects off a medium that is denser, it changes phase but not wavelength; if it reflects off a medium that is less dense, it changes neither wavelength nor phase
Diffraction
the spreading of light that occurs when a wave bends around the edges of an object or opening; significant diffraction occurs when the size of the object or opening is on the order of the wavelength or smaller
Young’s double-slit experiment
light is projected onto a screen with 2 small slits, the light waves diffracting through the two slits interfere with one another and produce a predictable pattern of alternating light and dark bands (maxima and minima)
Diffraction grating
a series of many small slits that diffracts a light source into its component colors; spread out from shorter wavelengths to longer wavelengths; the more rulings (slits) a grating has, the narrower and more defined each maximum and the wider the dark regions between the maxima
X-ray diffraction
x-rays that are projected at a crystal scatter and create regular interference patterns unique to the structure of the crystal
