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Examkrackers Physics: All Lectures
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Gravity
Terms in this set (232)
scalar
a physical quantity that has magnitude. i.e. time
vector
a physical quantity with both magnitude and direction i.e. displacement, velocity, and acceleration
how do you add vectors?
the head of one arrow meets the tail of the second, the line drawn from the tail of the first and the head of the second is your added vector
how do you subtract vectors?
place the heads of the two vectors together, the line drawn from the tails of the vectors is your subtracted vector
component vector
are always at right angles and are equal to the original vector
how do you find lengths of component vectors?
the pythagorean theory A^2+B^2=C^2 and SOHCAHTOA
what are characteristics that describe motion
distance, displacement, speed, velocity, and acceleration
what is displacement?
distance with the added dimension of direction
what is velocity?
m/s; speed with the added direction of displacement v=d/t
instantaneous velocity
the speed of an object at any one moment in time
acceleration
the rate of change in velocity a=v/t
what is the acceleration of constant velocity?
0
linear motion equations only apply to objects that are experiencing what?
constant acceleration
what is the slope at any point on a displacement vs. time graph?
the instantaneous velocity at that particular time
an upward slope on a displacement vs. time graph?
positive velocity
a strait line has a constant slope on a displacement vs. time graph indicating what?
constant velocity
a strait horizontal line on a displacement vs. time graph has what kind of slope?
0
a curved line with a changing slope on a displacement vs. time graph indicates what?
acceleration/ changing velocity
what is the slope at any point on a velocity vs. time graph?
instantaneous acceleration at that particular time
an upward slope on a velocity vs. time graph?
positive acceleration
What is the difference in area on a velocity vs. time graph as compared to a displacement vs. time graph?
the area is displacement and means something
what does the area beneath the x-axis in a velocity vs. time graph represent?
negative displacement
projectile motion
the movement of an object through the air along a curved path, an example of uniformly accelerated gravity
what is the formula to find peak height of the objective
v=(square root) 2gh
what does v represent in v=(square root) 2gh?
the initial vertical velocity or visin0
even when the projectile is motionless what is acceleration equal to?
gravity (g)
what is inertia?
all objects have the tendency to remain in their present state of motion
mass
the quantitative measure of an objects inertia
weight
the gravitational force that an object experiences when it is close to a much larger body; N; mg
center of mass
the single point at which all of the systems mass can be considered to be concentrated
net force
the sum of all forces acting on an object; creates acceleration and causes changes in motion
what are the three possible forces that causes an object to move?
gravitational, electromagnetic, and contact
What is Newton's Second law?
F=ma
Newton's 3rd law?
for every action their is an equal and opposite rxn
gravitational force
the attractive force that every mass in the universe exerts on every other mass in the universe
formula for gravitational force
F=Gm1m2/r^2
normal force
perpendicular to the surface that applies it
how to calculate normal force on an inclined plane?
mgcos0
how to calculate net force on a frictionless inclined plane?
mgsin0 due to gravity and normal force
friction
a force that opposes relative motion
what happens to an objects acceleration when undergoing air resistance when its mass increases?
it decreases
Hooke's law
a force that results from compressing or stretching an object F=-kx
rotational motion
forces acting at points other than an object's center of mass
translational motion
forces acing on an objects center of mass
torque
the ability of a force to produce rotational motion
equilibrium
no net force, no net torque= constant velocity
how to calculate the magnitude of torque?
t=Frsin0
the greater the net torque on an object, the greater the what?
its rotational acceleration
when does torque increase?
when the component of the force acting perpendicular to the position vector increases and when the distance between the point of application of the force and the point of rotation increases
what are the two types of equilibrium?
static- if all velocities are 0, dynamic- if any velocities are nonzero
how do you balance the two sides of an equation that is not in equilibrium?
add ma to the side with less force; Fup+ma=Fdown
open system
allows exchange of energy and mass with its surroundings
closed system
allows exchange of energy with its surroundings but not exchange of mass
isolated systems
allows no exchange of energy or mass with the surroundings
unit of energy
joule (J)= 1kgm^2/s^2= 1Nm; is scalar
mechanics
the study of bodies, the forces that act on them, and the motion that they experience
what are the two types of energy?
mechanical-energy of a macroscopic system and non mechanical- energy of a microscopic system
what are the two types of mechanical energy?
kinetic (K)- the energy of motion; K=1/2mv^2 and potential energy- the energy of position
what are the types of potential energy?
gravitational- U=mgh; electrical, and elastic(Ue =1/2kx^2
what are the two types of energy transfer?
heat(q) and work(W); heat- the energy transferred between a system and its surroundings due to a difference in temperatures
first law of thermodynamics
W+q=E=K+U; any change in the total energy of a system is due to either work or heat
work-kinetic energy theorem
W=K; it is only true when all energy transfer results only in a change to kinetic energy
work formula
W=fdcos0=K+U
what value is assigned to any energy going into a system or if the force acts in the direction of displacement?
positive
power
the rate of energy transfer P=W/t
conservative forces
mechanical energy before equals mechanical energy after
law of conservation of mechanical energy
when only conservative forces are acting the sum of mechanical energies remains constant
non conservative forces
does work on a system; the mechanical energy of a system changes
machines
reduce the force required to do a given amount of work; don 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; reduces the force needed by increasing the distance over which the force is applied; based on the principle of torque
pulley
allows force to act over a greater distance so the same amount of work can be done; uses tension
fluid
is a liquid or gas; molecule bonds are constantly breaking and reforming due to high kinetic energy of the molecules
extensive properties
properties concerned with quantity like mass and energy
intensive properties
concerned with the intrinsic nature of a substance and thus do not change with the quantity of a substance like density and pressure
density (p)
the heaviness of a fluid or how much mass a fluid contains in a specified volume (V); formula p=m/v; kg/m^3
ideal gas law
PV=nRT; gases are incompressible, liquids and solids are not
specific gravity
the density of a substance compared to the density of h2o; s.g.=psubstance/ph2o;
fluid pressure
the pressure experienced by the object as an impulse of molecular collisions; P=F/A=pgy (Pa)
what kind of forces does a fluid at rest only experience?
perpendicular forces
Pascal's principle
states that pressure applied anywhere to an enclosed incompressible fluid will be distributed undiminished throughout that fluid
hydraulic lift
a simple machine that works via Pascal's principle; F1d1=F2d2 and F1/A1=F2/A2
buoyant force
the force that a standing fluid exerts on any object that is floating, submerged, or sunk in the fluid F=pVg
Archimedes Principle
the upward buoyant force is equal in magnitude to the weight of the displaced fluid
when does and object float
it displaces a volume of fluid equal to that of its own mass pobject/pfluid=Vfluid/Vobject
describe buoyancy on a submerged object
it displaces a volume of fluid equal to its own volume and experiences an upward buoyancy force equal in magnitude to the downward gravitational force
describe buoyancy on a sunken object
a sunken object displaces a volume of fluid equal to that of its own volume Vobject*pfluid/pobject= mfluid/mobject
what part of an object does the buoyancy force act on?
the point where the center of mass would be if the object had uniform density
what are the two types of motion of molecules of a moving fluid?
random translational motion- contributes to fluid pressure as in a fluid at rest and uniform translational motion- shared equally by all the molecules at a given location in a fluid
why is their less pressure in a liquid moving through an opening?
fewer collision
what are the characteristics of an ideal fluid?
no viscosity, incompressible, lack turbulence, and they experience irrotational flow
viscosity
a fluids tendency to resist flow
formula for volume rate flow
Q=Av
mass flow rate
I=pAv
streamline
a pathway followed by a hypothetical fluid particle
Bernoulli's equation
the sum of the pressure, kinetic energy per unit volume, and potential energy per unit volume of a fluid remains constant thoughout that fluid; P+1/2pv^2+pgh=const.
formula for the velocity of a fluid coming from a spigot
v=squareroot(2gh)
venture effect
the decrease in pressure that occurs when a fluid flows into a constricted region of a pipe
drag
a force working against flow
formula that shows that fluid moves from high to low pressure
P=QR
Poiseuille's Law
commonly used to predict the flow rate of real fluids; Q=P*pir^4/8nL
surface tension
the intensity of the intermolecular forces of a fluid per unit length
what affects intermolecular forces
temperature (higher temperature weaker surface tension) and the fluids properties
capillary action
fluid pulled up a thin tube
what are the two types of capillary action
adhesive and cohesive forces
adhesive forces
forces between the molecule of the tube and the fluid molecules
cohesive forces
the intermolecular forces responsible for surface tension; stronger cohesive forces= convex surface
two types of electric forces
exists between two charges; attractive-different charges and repulsive-same charge
units of charge
coulombs (C)
coulombs law
the magnitude of the force of the repulsion or attraction between two charged objects; F=k*q1q2/r^2
universal law of conservation of charge
the universe has no net charge
center of charge
the point from which the charge generated by an object or system of objects can be considered to originate
field
some type of distortion or condition in space that creates a force on a charge (or a mass)
electric field
the electrostatic force per unit charge; E=kq1/r^2; N/C or V/m
potential energy (U) of a charge
U=qEd
Voltage (V)
is the potential for work by an electric field in moving any charge from one point to another V=Ed
equipotential surface
all points are of the same voltage
electric dipole
created by two equal charges with equal magnitude
conductors
such as metals that allow for electrons to flow relatively freely
resistors
poor conductors that hold electrons tightly in place like diamond and glass
current
moving charge given in amps (A) or C/s
drift speed
uniform translational movement opposite the direction of the current
circuit
a cyclical pathway for moving charge, a battery provides the potential difference needed to maintain charge flow
resistivity (p)
resist the flow of charge
resistance (R)
the quantitative measure of an object of a particular shape and size to resist the flow of charge and is measured in ohms R=p*L/A
Ohms law
electric current (i) is equal to potential difference or voltage divided by resistance; i=V/R
battery, what is it rated by?
adds energy to a circuit; rated by the electromotive force (EMF) for voltage
cathode
the electrode in a battery with the higher potential
anode
the electrode in a batter with a lower potential
the voltage of a battery id found by?
the difference between the cathode and anode
what happens when a capacitor is added to a circuit
some of the energy generated by the battery can be stored
parallel plate capacitor
two plates made from conductive material that are separated by a very small difference
formula for amount of capacity
C=Q/V
the energy (U) stored in any shape capacitor is give by what formula?
U=1/2QV=1/2CV^2=1/2Q^2/C
dielectric constant (k)
the substance between the plates of a capacitor; work is done by the dielectric and energy is stored in the dielectric
series
any two components not separated by a node
parallel
single components in alternative paths connecting the same nodes
when resistors are in a series,
their total resistance is the sum of their resistors
when resistors are in parallel,
their effective resistance can be arrived at through 1/Reff=1/R1+1/R2....
when capacitors are in a series,
1/Ceff=1/C1+1/C2...
when capacitors are in parallel,
Ceff=C1+C2...
ammeter
an instrument that measures the current flowing through a circuit
voltmeter
an instrument that measures the potential difference between any two points on a circuit
magnetic field
created by a magnet, measured in units of telsa, T; examples : electromagnetic radiation, nuclear magnetic resonance, MRI; is non conservative
what kind of charges produce magnetic fields?
only moving charges; static electric field produce no force on a magnet
north and south poles
opposite charges attract and similar ones repel
what creates magnetic fields
all currents
which is stronger? magnetic force or gravitational?
magnetic
the magnitude of force on a magnetic field?
F=qvBsin0
what does a magnetic field exert on a charged particle
a centripetal force
faraday's law
any change in the magnetic environment of a coil of wire will cause a voltage to be induced by the coil
production of sound
occurs via the vibration of a source (i.e. vocal cords)
wave
the propagation of a vibration from one point to another; the transfer of energy from one point to another
oscillations
regular variations
mechanical waves
require a medium through which to travel; i.e. sound waves
electromagnetic waves
do not require a medium through which to travel; propagate in vacuo; i.e. light
types of mechanical waves
transverse- the medium is displaced perpendicularly to the direction of the wave propagation i.e. a wave on a string, longitudinal- one in which the medium is displaced parallel to the direction of the wave propagation i.e. sound wave
velocity of a wave
the distance over which waves travel per unit time v=fλ
wavelengthλ
the distance from any point in the wave to the point where the wave begins to repeat itself
frequency f
the # of wavelengths that pass a fixed point in a second; s^-1 or Hz
period T
the time it takes the wave to travel the distance of one wavelength T=1/f
what dictates velocity
its medium
when a wave changes medium what happens to its velocity?
it changes
what two characteristics of a given medium determine the velocity of waves traveling through it
the mediums elasticity and the mediums inertia. increase in elasticity increase in velocity, increase in inertia decrease in velocity
what does temperature do to velocity?
increase temperature= increase velocity
elasticity
the measure of how quickly disrupted molecules will bounce back to their original shape; dictated by the strength of intermolecular forces
how does inertia increase
as mass and density do
what is the order of velocity of sound in a liquid, solid and gas medium fastest to slowest?
solid>liquid>gas
on a sine graph how is wavelength measured?
from either trough to trough or peak to peak
amplitude A on a sine graph
represented as the distance between the x axis and either the top or the bottom of a trough; changes as waves change medium
what does displacement refer to for transverse waves?
displacement of the medium perpendicular to the direction of the propagation
what does displacement refer to for longitudinal waves?
displacement of the medium parallel to the direction of the propagation
interference
the superposition of waves
types of interference
constructive- when the sum of the displacements results in a greater displacement, destructive sum results in a smaller displacement
phase
a horizontal shift of a wave on a Cartesian graph
sound
the transfer of energy through oscillations between high and low pressure
pitch
a measure of how "high" or "low" a note sounds; correlates with frequency
intensity I
the power of a wave, average rate of energy transfer per unit area; units in W/m^2; I=@pi^2pf^2A^2v
intensity level
a measure of loudness using a logarithmic scale in decibels (dB) B=10logI/Ii with Ii being the threshold intensity of human hearing
audible waves
human hearing range; between 20 and 20,000 Hz
ultrasonic waves
waves with frequencies above this range
wave pulse
a single wavelength
antinodes
the points intersected at the two vertical lines that experience maximum constructive interference
standing wave
the string would hold perfectly still at the nodes and move violently up and down at the sntinodes
resonance
the condition where the natural frequency and the driving frequency are equal;
resonance in pipes and strings
if both ends are open/unfixed there is an antinode at each end, if both are closed/fixed theres a node, if one end is open and the other is closed the open end will have a antinode
attenuation or damping
the decrease in the intensity of a wave through the medium i.e reflection and absorption
the doppler effect
the change in perceived frequency that occurs when a wave source and its observer move towards or away from one another
how to calculate doppler effect
assume observer is not moving, if the source is moving towards an object label that direction negative with a minus sign for vs, check the direction that the observer is moving, if its the same use the same sign for vo if different use the opposite sign
can reflection of sound from a moving object cause a doppler effect?
yes
beat frequency
fbeat= fo-fs
the speed of a vehicle
v=c(delta)f/2fs
shock wave
a conical wave front produced when the velocity of sound source exceeds the velocity of the sound wave
light
the transfer of energy through alternating electric and magnetic fields
wave theory
while the energy transformation properties of light are best described as a particle theory
photons
the light emitted by electrons; pulses of electromagnetic radiation that can be thought of as localized particles of energy
the energy change of electron E formula
E=hf
fluorescent light
when the electron loses energy, it falls into one of those intermediate states
incandescent light
exhibiting a continuous range of wavelength
visible light range
all wavelengths from 390
10^-9 m to 700
10^-9m
what color does shorter wavelengths correspond to
violet
what color does longer wavelengths correspond to
red
ultraviolet
beyond violet
infrared
beyond red
the speed of light in vacuo
constant and equal to the ratio of the magnitudes of the electric field x=E/B=3*10^8 m/s
when a wave propagates through media what does it undergoe?
absorption
what determines the color that you see of an object?
the color is determined by the colors that are reflected and not absorbed
when is light polarized?
when its electric and magnetic fields are oriented in a particular way
what does nonpolarized light do in all directions?
vibrates
circularly polarized light
when it consists of electric fields of constant magnitude that change direction in a rotary manner
how is a wave altered when it meets an interface between two media?
through reflection and refraction
when is a wave reflected
at a boundary between media, it bounces back to return into the medium from which it came
angle of incidence
the angle at which a wave strikes an interface
angle of reflection
an angle at which it reflects
what happens to the angles of incidence and reflection when light reflects off of a plane surface?
they are equal
index of refraction (n)
the speed of light in a vacuum, c, to the speed of light in a particular medium, v. n=c/v
what is the refraction for water and glass
1.3 and 1.5
Snells law
the extent to which a change in speed will bend a light ray; n1sin01=n2sin02
angle of refraction
measured from a line normal to the interface between media
total internal reflection
if the angle of incidence is large enough, all photons will be reflected at the angle of reflection, and none will refract
formula fir critical angle
0critical=sin^-1(n2/n1)
dispersion
the separation of light into different frequencies due to their different indices of refraction in a medium; can occur due to refraction
thin film interference
occurs when a thin layer of a substance is placed between two layers of another substance that has a different index of refraction
thin film reference is a result of..?
phase changes associated with reflections off media that are more dense, path length differences, and wavelength changes associated with changes in media
diffraction
the spreading of light that occurs when a wave bends around the edges of an object or opening
what are the three ways that light bends?
refraction, reflection, and diffraction
which defracts more longer or shorter wavelengths?
longer
Young's double slit experiment
light is projected onto a screen with two small slits
coherent light
able to be forced into a parallel beam that spreads and weakens very little over great distances
diffraction grating
a series of many small slits that diffracts a light source into its component colors
x-ray diffraction
x-rays that are projected at a crystal scatter and create regular interference patterns unique to the structure of the crystal
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