Physics Flashcards
What are examples of scalar quantities?
speed, pressure, energy, and mass
What is the equation for the Y-axis component of a vector?
Y axis component = Magnitude x (sin θ)
What is the equation for the X-axis component of a vector?
X axis component = Magnitude x (cos θ)
Given the X and Y components of a vector, how do you find the resultant magnitude?
Pythagorean Theorem
How do you subtract two vectors?
You make the direction of the vector being subtracted in the opposite direction than it was going. Then you add the two vectors
What is the cross product of A x B?
A x B (sin θ between them)
What is the dot product of A dot B?
A x B (cos θ between them)
How will you remember that the cross product involves the sin θ between the vectors?
The CROSS is where SIN was destroyed
How does the right hand rule apply to the cross product A x B = C?
- Your thumb points in the direction of the first vector (A)
- Your fingers point in the direction of the second vector (B)
- Your palm will now automatically face in the direction of the resultant vector (C)
If a man travels 100 yards east and then 100 yards west, what is his displacement and what is the distance he traveled?
Displacement- 0 yards
Distance- 200 yards
What are the SI units for the velocity of an object?
m/s (meters/ second)
Why will the instantaneous velocity of an object always equal the instantaneous speed?
Because instantaneous velocity is found at a specific moment in time rather than compared to the change in time
What is the equation for the velocity of an object?
V = ΔX/Δt V= displacement/ time
What is a force?
A push or a pull on an object that causes an acceleration of that object
What is the SI unit for force and what are its derived units?
Newton = (kg)(m)/ s^2
Why does the force that gravity exerts on an object decrease as you go higher up on a mountain?
Because the force of gravity is inversely proportional to the distance between the two object’s center of mass
What is the equation for gravitational force?
Fg = Gm1m2/ r^2 Where: G = gravitational force constant m1 = mass of object one m2 = mass of object two r^2 = distance between the two objects center of mass
What is the gravitational force constant and what are its units?
G = 6.67 x 10^-11 (N x m^2/ kg^2)
What is the inequality that describes the force of static friction?
0 ≤ Fs ≤ UsN
Where:
Fs = force of static friction
Us = coefficient of static friction which is different for every surface
N = normal force between the two touching components
What is larger for the surface of sandpaper, the coefficient of static friction or the coefficient of kinetic friction?
Static friction coefficient is always higher
When does kinetic friction play a role in resisting movement between two objects?
When the objects are sliding against each other (ex. sandpaper against wood)
What is the equation for the force of kinetic friction?
Fk = UkN
Where:
Fk = force of kinetic friction
Uk = coefficient of kinetic friction which is different for every surface
N = normal force between the two surfaces
What is the difference between mass (m) and weight (Fg)?
Mass- is the measure of an object’s inertia or its the amount of matter in an object
Weight- is the gravitational force on an object’s mass
What is the equation for the weight of a person?
Fg = mg
Where:
Fg = weight
m = mass of that person
g = gravity that a person is experiencing
(Note the similarities to the equation for force)
What is the equation for the acceleration of an object?
a = ΔV/Δt
What are the SI units for the acceleration of an object?
m/s^2 (meters/ seconds squared)
What is newton’s first law?
If an object with a constant velocity (a = 0) with mass (m) has no force acting upon it (F) then it will remain at rest. This is the law of inertia
What is newton’s second law?
F = ma Where: F = force m = mass a = acceleration (Thus an object needs a forced applied to experience an acceleration)
What is newton’s third law?
The force that one object has on another (A on B) must be equal and opposite to the force that the other object has on it (B on A)
How does jumping while on earth apply to newton’s third law?
Well the force the earth has on us must equal the force that we have on the earth. However, since our mass is far less than earth then we accelerate toward it far faster than it accelerates toward us
What kinematic equation would I use if I was given the initial velocity, acceleration, and reference time, and was then told to find the velocity of the object at that specific time?
V = Vo + at
What kinematic equation would I use if I was given the initial velocity, acceleration, and reference time, and was then told to find how far the object has been displaced from its initial position at that specific time?
X = Vot + at^2/ 2
What kinematic equation would I use if I was given the initial velocity, displacement of the object, and acceleration of the object, and then was told to find the velocity of the object squared?
V^2 = Vo^2 + 2ax
What kinematic equation would I use if I was given the velocity and time and then told to find the displacement of the object at that time?
X = vt
How is terminal velocity reached?
At a certain time after falling, an object’s drag force (created by air resistance) will equal the weight of the object thus its velocity will remain constant
What is the first step to solving projectile motion problems?
Break the resultant vector into its X and Y components
In a projectile motion problem is there acceleration in the X direction? What about the Y direction?
Because there is no constant force in the X direction, there is no acceleration. However, in the Y direction the force of gravity is constant (9.8 m/s^2)
What is the first step in solving an inclined plane problem?
Break the resultant vector into a component that is perpendicular to the plane and a component that is parallel to the plane
In uniform circular motion, where is an object’s instantaneous velocity always pointing?
Instantaneous velocity will always point tangent to the the circular path
What is the force that keeps a car from flying off a racetrack when it goes around a tight turn?
Centripetal Force (always points toward the center of the circle) specifically caused by the friction of the tires in this example
Although not obvious at first, as a car drives in a circular racetrack it is constantly accelerating toward the center of the circle. What is this acceleration called?
Centripetal Acceleration
What is the equation for the force that causes centripetal acceleration?
Fc = mv^2/ r
What is the equation for torque?
t = rf (Sin angle) Where: t = torque r = distance force applied form fulcrum f = force
If all the torques acting on an object cancel out and equal zero then that object is said to be in what?
Rotational Equilibrium
What is energy?
The measure of somethings ability to do work
What is the equation for the energy associated with a moving object?
Kinetic Energy = 1/2 mv^2
Where:
m = mass
v = speed
As an objects mass increases, while its velocity stays the same, what happens to its kinetic energy?
Its kinetic energy increases because the larger size will allow it to do more work
What is the SI unit for energy and what are its derived units?
Joule = kg x m^2/ s^2 = N x m
What does the v stand for in the kinetic energy equation and why is this important?
v = speed and this is important because it shows that the direction an object is traveling does not effect its kinetic energy
What is the equation for gravitational potential energy?
U = mgh Where: m = mass g = acceleration due to gravity h = height above a datum (usually the ground)
What is the equation for elastic potential energy?
U = 1/2 kx^2
Where:
k = spring constant (measure of how stiff a spring is)
x = displacement of spring from equilibrium
When you combine the Potential and Kinetic energies of an object what is the resultant?
The Total Mechanical Energy (E)
When an object undergoes a nonconservative force why can the equation E = U + K NOT be used?
Because a nonconservative force would allow for energy to leave the system via another form (thermal energy, light energy)
When an object undergoes a nonconservative force the object will lose some of its total mechanical energy. Where will this energy be transferred to?
This energy is the work being done by the system
What is work? What are some examples?
Work is the transfer of energy from one form to another (ex. work is done on a piston that converts mechanical energy of steam molecules {pressure} to the movement of whatever the piston is attached to)
What is the equation for work?
W = F * D W = F x D x (cos θ) Where: W = work F = magnitude of force D = magnitude of displacement through which the force is applied
What is the SI unit for work?
Joule
What does the area under a P/V graph for a moveable piston and gas system indicate?
The work being done by the gas. As the gas expands it pushes the piston by changing its volume
For a isobaric process system containing a chamber of gas connected to a piston, is there any work being done by the gas on the piston if gas is added to the chamber?
Yes; because as the volume of the gas increases the piston of the system must move out to keep the pressure of the chamber the same
What is the equation used to find the work done by an isobaric system?
W = PΔV
Where:
P = pressure
ΔV = change in volume of the gas chamber
What is power defined as?
The rate at which work is being done. Thus it is the rate at which energy is transferred from one form to another. (ex. think of lifting a box really fast where you are doing work on the box by changing the chemical energy of your bodies cells into potential energy of the box at a fast rate)
What is the equation for power?
P = W/t
OR
P = ΔE/t
What is the SI unit for power?
Watt = J/s
What is the equation used to connect work to the energy of an object?
The Work-Energy Theorem
Wnet = Kf - Ki
This is seen in your car. As the net work of frictional forces of your brakes add up to cause a change in the kinetic energy of your car
When is it helpful to use the work-energy theorem equation?
When you don’t know the magnitude of the forces or displacement acting on an object
What is the equation for mechanical advantage?
Mechanical Advantage = Fout/ Fin
Where:
Fout = force exerted on an object by a simple machine
Fin = the force applied to the simple machine
Conceptually, what do simple machines actually do?
They make it easier to apply high forces to objects by increasing the distance by which that force is applied
What is the equation to find the efficiency of a simple machine?
Efficiency = Wout/ Win
Where:
Wout = load x load distance
Win = effort x effort distance
What is the relationship between temperature and heat?
Heat (transfer of thermal energy) flows from higher temperature objects to lower temperature ones (ex. from a hot pan to a hand)
What does the zeroth law of thermodynamics state?
That if objects A and B are in thermal equilibrium and objects B and C are in thermal equilibrium, THEN objects A and C are in thermal equilibrium as well meaning that no heat flows between them
What is the freezing point of water in Kelvin?
273 K
What is the freezing point of water in Celsius?
0 °C
What is the freezing point of water in Fahrenheit?
32 °F
What is the boiling point of water in Kelvin?
373 K
What is the boiling point of water in Celsius?
100 °C
What is the boiling point of water in Fahrenheit?
212 °F
What is the typical human body temperature in Celsius?
37 °C
What is the typical human body temperature in Fahreneheit?
98.6 °F
What does the third law of thermodynamics state?
That the temperature of a perfectly organized crystalline object is 0 Kelvin?
What is the equation for thermal expansion? What is the mnemonic for remembering this?
ΔL = αLΔT Where: ΔL = change in length of the object α = the coefficient of linear expansion L = original length ΔT = change in temperature When an solid's temperature changes, its length changes aLOT
What is the equation for the volumetric thermal expansion for a liquid? What is the mnemonic for remembering this?
ΔV = βVΔT Where: ΔV = change in volume of liquid β = coefficient of volumetric expansion V = original volume ΔT = change in temperature When an liquids temperature changes, its volume changes like a Boat
How is an isolated system different from a closed system?
Isolated systems don’t exchange either energy or matter with the surroundings
closed systems don’t exchange matter but do exchange energy with the surroundings
What does the second law of thermodynamics state?
That for every spontaneous process the total entropy of the Universe must increase
What does the first law of thermodynamics state? What is the equation that mathematically shows this?
That when a system loses or gains internal energy, it must be do either to heat/work being done by/on the system ΔU = Q - W Where: Q = energy transferred as heat W = energy transferred as work
In the equation for the first law of thermodynamics, if work is being done by the system what sign (+ or -) will the work term be given? What effect will this have on the total internal energy?
Work will be given a positive value
ΔU = Q - (+W)
The total internal energy will thus decrease
In the equation for the first law of thermodynamics, if work is being done on the system what sign (+ or -) will the work term be given? What effect will this have on the total internal energy?
Work will be given a negative value
ΔU = Q - (-W)
The total internal energy will thus increase
How many joules are in one Calorie?
4,184 Joules
As you touch a hot stove the particles of the stove are directly touching your skin and causing a searing pain. What type of heat transfer occured?
Conduction
On a hot day it feels really nice if you stand in front of a big fan. What type of heat transfer is the fan generating?
Convection
Many cold weather clothing companies have started to put reflective patches on the inside of their jackets. What type of heat transfer are they trying to prevent?
Radiation
What is the measure of the amount of heat transfer required to raise the temperature of a substance by
1 °C
Specific Heat
If you are adding high amounts of heat energy to an object but the temperature is remaining unchanged, what is likely occurring to the substance?
A Phase Change (ice to water)
Given the specific heat of a substance, what equation would help determine how much heat has been gained or lost by that substance?
q = mcΔT
Where:
m = mass of substance
c = specific heat
The particles in a steel beam are moving around very very fast, this object is said to have high what?
Thermal Energy
During the melting of an ice cube to water there is no change in the temperature of the ice cube do to the heat transfer causing an increase in potential energy (more randomness in water). What equation is used to find the heat needed for a substance to undergo a phase change?
q = mL
Where:
m = mass of substance
L = heat of transformation/latent heat
What are the units for the heat of fusion of a substance?
J/Kg (note similarity to specific heat but there is no change in temperature)
What is the process of going from a liquid to a solid called?
Freezing (or solidification)
What is the process of going from a solid to a liquid called?
melting (or fusion)
What is the point at which a substance starts to change from a solid to a liquid
melting point
What is the amount of heat transfer required for a substance to change from a solid to a liquid
Heat of Fusion
What is the amount of heat transfer required for a substance to change between a liquid and a gas?
Heat of Vaporization
What is the equation to find the change in entropy of a substance?
ΔS = Qrev/ T Where: ΔS = change in entropy Qrev = heat gained or lost in a reversible process T = temperature in kelvin
What is the equation for denisty?
p = m/v
Where:
m = mass
v = volume
What are the SI units for density?
Kg/m^3
What is the density of water?
1 g/cm^3
OR
1000 Kg/m^3
What equation can be used to find the weight of any volume of a substance?
Fg = pVg Where: p = density V = volume g = acceleration due to gravity
What is the density (in kg/m^3) of a substance that has a specific gravity of .877?
Specific Gravity = p/ density of water in (g/cm^3)
= 877 kg/m^3
What is the equation for pressure?
P = F/A Where: P = pressure F = magnitude of the normal force A = area force is applied
What is the SI unit for pressure? What are its derived units?
Pascal (Pa) with the units N/m^2
How many pascals are in 1 atm?
101.325 Kilopascals
How many mmHg are in 1 atm?
760 mmHg
How many torr are in 2 atm?
1520 torr
What is the difference between absolute and atmospheric pressure?
The pressure that is pressing down from the atmosphere and changes with elevation. On the other hand, absolute pressure is a measure of the total pressure pushing down on a submerged object
Will a person on top of a mountain experience a higher or lower pressure?
A lower atmospheric pressure
What is the equation for absolute pressure?
P = Po + pgz Where: P = absolute pressure Po = incident or ambient pressure above the liquid p = density of the liquid g = acceleration due to gravity z = depth of the object
How is gauge pressure different from absolute pressure?
Gauge pressure only considers the pressure that exceeds atmospheric pressure (ex. the pressure inside a bike tire)
What is the equation for gauge pressure?
Absolute Pressure - Atmospheric Pressure (note when ambient pressure = 1 atm gauge pressure is pgz)
What does pascals principal state?
That the pressure exerted on an incompressible liquid would be the same everywhere the liquid is touching
What is pascals principal used for in modern machinery?
It is how hydraulic systems work to help machines move big heavy objects (Trac-hoe)
What is the equation to find the force created by a car lift that pushes down a force with a small piston into a chamber of fluid that has a very large piston on the other side?
F2 = F1 (A2/A1)
What does Archimedes principle state in laymen’s terms?
That a partially or completely submerged object will be pushed upwards by a force equal to the weight of the fluid it displaces
What is the equation for Archimedes principle?
Fb = pVg Where: p = fluids density V = volume displaced g = acceleration due to gravity (NOTE how similar the equation is to the weight of a substance. That is because Fb on object and Fg of fluid are the same)
If a fluid is flowing with laminar flow through a pipe what effect will changing the radius of the pipe have on the flow rate?
A slight change in the radius of the pipe will cause the flow rate to be WAY higher (r^4)
What does the continuity equation tell us about liquids?
Liquids will flow more quickly through narrow passages and more slowly through wide passages
What is the continuity equation?
Q = v1a1 = v2a2 Where: Q = flow rate v = linear speeds of liquid a = cross-sectional area
How can the conservation of energy be related to a liquid traveling through a pipe?
Bernoulli’s equation (look it up damnit)
According to Bernoulli’s equation, as the speed of a fluid increases what happens to the pressure in that area?
The pressure decreases (ex. smoke only goes out the window when a car is moving)
This is because if you restrict the movement of the fluid (slower speed) then that energy has to be translated elsewhere (increased pressure)
What is a ground in terms of electrostatic charge?
It is something that allows charge to be returned to earth
What is the charge of a proton in coulombs?
1.6 x 10^-19 C
What equation quantifies the electrostatic force between two charges?
Coulomb's Law Fe = kq1q2/ r^2 Where: Fe = magnitude of electrostatic force k = Coulomb's constant q1/q2 = magnitude of the two charges r = distance between charges
What is Coulomb’s constant and units?
8.99 x 10^9 (N x m^2/C^2)
As the distance between two charges increases, what happens to the force between them?
It decreases because it has an inverse relationship to r^2
What is the difference between a source charge and a test charge?
The source charge (Q) is the charge that is creating the measured electric field while the test charge (q) is the charge placed in the field to “test” its strength
What are the two equations for finding the electric field generated by a source charge?
E = Fe/q
OR
E = kQ/r^2
How is electric potential energy defined?
It is defined as the energy that a charge will move with if it is released from a specific position
What is the equation for electric potential energy
U = kQq/r
If we were to measure the electric potential energy of a negative charge that was nearby another negative charge, would the electric potential energy be negative or positive?
Positive (they would be less stable due to repulsive nature)
If we were to measure the electric potential energy of a negative charge that was nearby a positive charge, would the U be negative or positive?
Negative (they would be more stable because of the attractive nature)
What is the SI unit for electric potential and its derived units?
1 Volt = 1 J/C
What is the equation for the electric potential?
V = kQ/r
What is the SI unit for the magnitude of a magnetic field? What are its units?
Tesla = (N x s) / (m x C)
How many gauss are in one tesla?
1 T = 10^4 gauss
What is the difference between diamagnetic, paramagnetic, and ferromagnetic?
Diamagnetic - have no unpaired electrons thus have no net magnetic field and do not become magnetized
Paramagnetic- have unpaired electrons in its orbitals thus it will become magnetic when placed in a magnetic field
Ferromagnetic- have unpaired electrons in its orbitals thus it will become strongly magnetic when placed in a magnetic field
Does any moving charge create a magnetic field?
Yes
What is the equation for the magnetic field created by a straight current carrying wire?
B = (UoI) / (2πr) Where: Uo = permeability of free space I = current running through the wire r = magnetic fields distance from the wire
What is the constant for permeability of free space? What are its units?
4π x 10^-7 (T x m/ A)
What is the equation for the magnetic field created by a loop of wire with a current running through it?
B = (UoI) / (2r) Where: Uo = permeability of free space I = current running through the wire r = radius of the loop
What is the sum of the magnetic and electrostatic forces acting on a charge called?
Lorentz Force
When a test charge is moving through a magnetic field what is the equation used to find the magnetic force acting on it?
Fb = qvB (Sin θ) Where: q = test charge magnitude v = magnitude of charges velocity B = magnitude of the magnetic field
If a charge is moving the the same direction as a magnetic field, will the field generate a force on it?
No; for a charge to experience a force it must be moving perpendicular to the magnetic field
How does the right hand rule apply to a magnetic field?
- Point your thumb in the direction of the velocity
- Point your fingers in the direction of the field lines
- Your palm will point in the direction of the force on the charge
What does the unit siemens measure?
Conductance
What is the sign convention for the measurement of current?
Current is seen as the direction of flow of a positive charge
What is the equation for current?
I = Q / change in time
How can current, resistance, and voltage related to a the flow of water?
Current- is the amount of water flowing past a point at a time
Resistance- is how easily water can flow through a certain part of the river
Voltage- is the direction of the water flow caused by the height of the starting point (a waterfall is a drop in voltage and water only flows down waterfalls)
What is the SI unit for current?
1 Amp = 1 C/s
What is the difference between direct current (DC) and alternating current (AC)?
DC- the charge only flows in one direction
What are the units for the electromotive force (emf)?
EMF is a voltage thus 1 V = 1 J/C
Where J/C indicates that voltage is measuring the energy that each coulomb is carrying
What does Kirchhoff’s junction rule state?
The current into a junction must equal the current leaving a junction
What does Kirchhoff’s loop rule state?
The starting voltage in a loop (emf) must equal the voltage drop off all the resistors along the way
What four properties of a resistor determine its resistance?
- Resistivity (property of the material used)
- Cross Sectional Area (the bigger it is the less it can resist current flow)
- Temperature (a higher temperature leads to a higher resistance)
- Length (the longer it is the longer the amount of time charge will flow through it)
What is the equation to measure the resistance of a resistor?
R = pL/A Where: R = resistance p = resistivity L = length of the resistor
What effect does an increase in temperature usually have on resistance?
It increases it
What is the equation for Ohm’s law?
V = IR
According to Ohm’s law, what effect does resistance have on the current running through it?
It lowers the voltage of the current running through it (i.e. it lowers the energy that the electrons had by lowering them down the waterfall)
According to Ohm’s law what does the measure of current running through a wire depend on?
I = V/R thus the current depends on the voltage drop that is experienced compared to the resistance of the wire
What is the power of a resistor conceptualized as?
The amount of energy that is dissipated from a resistor as current flows through it (such as the coils in a toaster)
What is the equation for the Power in terms of energy given off by a resistor?
P = IV = I^2R = V^2/R
IMPORTANT NOTE:
- remember that P = IV and that the other forms of the equation can be found by inserting Ohm’s law
For a set of resistors in a series what will the total voltage drop be?
The voltage drop will be equal to the total voltage drops caused by each resistor. This is because the current has no choice of where to go.
For a set of resistors in a series what will the total resistance be?
The resistance will be equal to the summed resistances of all the resistors because the charge has to go through all of them.
For a set of resistors in parallel what will the total voltage drop be?
The voltage drop through each resistor pathway will be the same. This is supported by the loop rule
For a set of resistors in parallel (R1, R2, R3) what will the total resistance be?
Because the current has a choice of which resistor to go through, the majority of the current will go through the resistor with the least resistance thus the total resistance would be
1/Rtotal = 1/R1 + 1/R2 + 1/R3
When placed in a circuit what do capacitors do?
They build up charge on a parallel plate that can be released later (ex. lighting is the build up of charge between earth and the atmosphere)
What is the equation for capacitance?
C = Q/V
If a capacitor is able to store more charge (higher Q) will it have a higher or lower capacitance?
Higher
What is the SI unit for Capacitance?
1 Farad = 1 C/V
When placed in a capacitor what does a dielectric material do?
It aids the capacitor in the storing of charge
What is the equation for the capacitance of a parallel plate capacitor? What is the mnemonic to remember this?
C = Ake0 / d Where: C = capacitance A = surface area of the plates k = dielectric constant (not always present) e0 = permittivity of free space d = distance between two plates
What is the permittivity of free space?
8.85 x 10^-12 (F/m)
How are capacitors in series and parallel different from resistors?
The equations are flipped
What is the difference between transverse and longitudinal waves?
Transverse- waves oscillate back and forth in a direction perpendicular to the propagation/direction of movement of the wave (ex. electromagnetic waves)
Longitudinal- waves oscillate back and forth in the direction of the propagation of the wave (ex. sound waves)
What is the frequency of a wave?
The number of wavelengths that pass a certain point in one second
What is the SI unit for the frequency of a wave?
1 Hertz (Hz) = 1 Cycle/s
What is the wavelength of a wave?
The distance between any two similar locations on a wave
What is the propagation speed of a wave and what is the equation to find it?
It is how fast the wave is traveling v = f λ Where: f = frequency λ = wavelength
What measurement is the inverse of frequency in that it measures the amount of seconds that pass for each cycle of a a certain wave?
Period = 1/f
What is the amplitude of a wave?
The distance that the crest oscillates from the equilibrium
If two waves have the exact same frequency, wavelength, and amplitude but the crest of one wave is at the trough of another while they are moving, what is the phase difference between them?
λ/2 or 180 degrees
What type of interference between waves is responsible for the effect that noise cancelling headphones have?
Destructive interference (the headphones play a sound that is directly out of phase with the external sound)
Explain a situation that will create a standing wave
One example is when a rope is attached to a firm anchor and then the other side is shaken at such a frequency that the wave appears to be stationary
What are the nodes and antinodes of a standing wave?
Nodes - points where the amplitude of the wave is zero
Antinodes - points where the amplitude is at its maximum
Why do some sounds, such as Rayland Baxter singing, sound really nice while other sounds, such as Brendan screaming do not?
Because Rayland Baxter sings with a pure tone (good timbre) while Brendan sings with multiple frequencies overlapping
What types of materials can a sound wave travel through and what can it not travel through?
Sound waves are longitudinal and require the oscillation of particles back and forth. For this reason sound can travel through any deformable medium but not through a perfect vaccum
What is the equation for the speed of sound through a medium?
v = sqrt (B/p)
Where:
B = bulk modulus which is the measure of a medium’s resistance to compression
p = density of the medium
Will a sound wave travel faster through air, water, or metal?
Metal- fastest
Air- Slowest
Will a sound wave travel faster through drywall (low density) or steel wall (high density)?
It will travel faster through drywall
What is the approximate speed of sound in air at 20 celsius?
343 m/s
What is the difference between infrasonic and ultrasonic frequencies?
Infrasonic- below 20 Hz
Ultrasonic- above 20,000 Hz
According to the doppler effect, if the source of a sound wave and the perceiver of that wave are moving toward each other, will the perceived frequency be higher or lower?
Higher
According to the doppler effect, if an ice-cream truck is driving toward someone but that person is running away from the truck at a rate faster than the truck, will the ice-cream truck’s songs be perceived as a higher or lower frequency?
Lower
What is the equation for the doppler effect? What is the mnemonic for the weird sign convention?
Look it up and check if you are right (sorry mate)
Remember to use the T-op sign for T-oward
If a sound wave has a high intensity, when it reaches our ears what do we characterize it as?
A loud sound
What is the intensity of a sound?
The rate of energy transfer per the surface area that is perpendicular to the wave (surface area of the eardrum for example)
What is the equation for intensity of a sound wave?
I = P/A
Where:
P = power
A = area
What are the units for the intensity of a wave?
Watts/m^2
What is a decibel mathematically?
β = 10 log (I/Io)
Where:
I = intensity of a specific sound
Io = threshold of hearing
What is the threshold of hearing?
1 x 10^-12 (W/m^2)
What is the equation for the wavelength of a standing wave for a specific length of string?
λ = 2L/n
Where:
L = length of string
n = the harmonic or the number of have wavelengths supported by the string
What equation would be used to find the possible frequencies in a wave on a string with a specific length and speed?
f = nv/2L Where: n = harmonic v = wave speed L = length of the string
What is the lowest frequency (longest wavelength) that can be supported by a given length of string called?
Fundamental Frequency or the First Harmonic
For a string anchored at both ends, how do you find the harmonic that the wave is in?
Count the number of antinodes
For a pipe that is open on both ends, how do you find the harmonic that a sound wave traveling through it would be in?
Count the number of nodes
For a pipe that is closed on one end, how do you find the harmonic that a sound wave traveling through it would be in?
Count the number of quarter wavelengths
What is the mnemonic for determining what harmonic a wave is in that is traveling through a string, open pipe, or closed pipe?
SANd is ON the Cheeks of my Queen
Strings (anchored)- count Anti Nodes
Open (pipe)- count the Nodes
Closed (pipe)- count the quarter wavelengths
On the electromagnetic spectrum what is the order of waves with the highest wavelength to the lowest wavelength?
- Long Radio Waves (Highest)
- AM/FM Radio Waves
- Microwaves
- Infrared
- ROYGBV Visible Light
- UV Rays
- X Rays
- Gamma Rays (Lowest)
On the electromagnetic spectrum, what is a way to remember that the relative frequencies of the various waves?
Things with higher frequencies than visible light are found outside the house (Gamma Rays, X Rays, UV Rays) while things that are found inside the house have lower frequencies than visible light (Infrared, Microwaves, Radio Waves)
What is the range of wavelengths for light that is visible to the human eye?
750nm (Red light) through 380nm (Violet Light)
The fact that light travels through pure water (or any homogenous medium) in a straight line is called what?
Rectilinear Propagation
If light travels from one medium to another medium but is not absorbed by the second medium, what has happened to the light?
Reflection
What is the equation for the law of reflection?
θ1 = θ2
Where:
θ1 = incident angle (angle the light came in at)
θ2 = reflected angle
What are all angles in optics measured from? (such as the incident and reflected angles)
The Normal which is a line draw perpendicular to the boundary of the medium
What is the difference between a real and a virtual image?
Real Image- the light reflected or changed in a medium actually converges where the image is seen
Virtual Image- the light reflected or changed in a medium only appears to be where the image is seen
When you look in a mirror and it appears as if you (Object) are standing as far away behind the mirror (Image) as you are from it what type of image is being produced?
Virtual
What is the center of curvature of a mirror and what symbol is used to indicate this point?
- It is conceptualized as the center of a concave of convex mirror if the mirror was a complete circle
- the symbol is (C)
What is the radius of curvature of a mirror and what symbol is used to indicate this?
- It is the distance from any point on the mirror to the center of curvature
- the symbol is (r)
For a concave mirror, where is the center of curvature located?
In front of the mirror
For a convex mirror, where is the center of curvature located?
Behind the mirror
What is the point at which light rays meet or appear to meet after reflecting or refracting off something? What is the symbol for this?
Focal Point (F)
What is the distance from a point on a mirror to the point where the light rays converge or appear to converge? What is the symbol for this?
Focal Length (f)
What equation would be used to find the image distance that a mirror produces?
1/f = 1/o + 1/i = 2/r Where: f = focal length o = object distance i = image distance r = radius of curvature
If an image produced by a mirror is found to have a negative distance, what type of image is this?
Virtual Image
If an image produced by a mirror is found to have a positive distance, what type of image is this?
Real Image
What is the ratio of the image distance compared to the object distance? What is the symbol for this?
Magnification (m)
What is the equation for the magnification that a mirror produces?
m = -i/o
If an image has a positive magnification value is it upright or inverted?
Upright
If an image has a negative magnification value is it upright or inverted?
Inverted (up side down)
If an image has a magnification value that is greater than 1 or less than -1, will it be larger, smaller, or the same size as the object?
Larger
If an image has a magnification value that is in between -1 and 1, will it be larger, smaller, or the same size as the object?
Smaller
If an image has a magnification value of -1 or 1 will it be larger, smaller, or the same size as the object?
Same Size
If an object is placed a focal length away from a mirror, where will the image be located?
It will not appear as the reflected rays will be parallel
Why do objects that are half-in an half-out of water appear to bend in the water?
Because the light that they emit is refracted as it changes mediums
What is the equation to find the index of refraction of a medium?
n = c/v Where: n = index of refraction c = speed of light in a vaccum v = speed of light in the medium
What is the equation used to find the angle that light rays will refract to when they pass into a new medium?
n1 Sin θ1 = n2 Sin θ2
When light enters a medium with a higher index of refraction, to what direction does the light bend toward?
Bends toward the Normal
When light enters a medium with a lower index of refraction, to what direction does the light bend toward?
Bends away from the Normal
What happens to a light ray that enters another medium at its critical angle?
It is refracted at 90 degrees from the normal
What happens to a light ray that tries to enter another medium at an angle higher than its critical angle?
It experiences total internal reflection
What is the equation to find the critical angle for a medium?
θc = Sin-1 (n2/n1)
How are lenses different from mirrors?
Lenses refract light twice (coming in and coming out) while mirrors reflect light
What is the difference between thin spherical lenses and real lenses?
Thin Spherical Lenses- thickness of lens is negligible and the mirror equations can be used
Real Lenses- thickness of lens matters and thus the lens maker’s equation must be used
What is the lens maker’s equation?
1/f = (n-1) (1/r1 - 1/r2)
What is the equation used to find the power of a lens?
P = 1/f
What is the process of light spreading out after it passes through a narrow opening?
Diffraction
In a single slit diffraction set up, what equation is used to find the location of the dark fringes that are present on the capturing screen?
a Sin θ = nλ Where: a = width of the slit θ = angle between center of lens and the dark fringe n = number of the fringe looking at λ = wavelength of incident wave
In a double slit diffraction set up, what equation is used to find the location of the dark fringes that are present on the capturing screen?
d Sin θ = (n + .5) λ Where: d = distance between two slits θ = angle between midpoint of two slits and the fringe n = number of the fringe looking at λ = wavelength of the incident wave
What does it mean when light is polarized?
All the waves are oriented in the same direction
What is the process by which a beam of photons can cause a metal atom to emit electrons known as? What is a very important example of this effecT?
The Photoelectric Effect
ex. the sun’s photons causing magnesium in plants to emit electrons
When a scientist measures the weight of a atoms nucleus, it is found to weigh less than expected. What is responsible for this?
Mass Defect- matter (protons and neutrons) are converted to energy (radiation, light, heat)
What is the equation for mass defect?
E = mc^2
What is the difference between fission and fusion?
Fission- nuclei separate or emit particles
Fusion- two small nuclei combine into a larger nucleus
What is the notation for the particle emitted in an alpha decay reaction?
A Helium nucleus (He) thus
4/2
When a neutron decays into a proton, what particle is emitted from the atom?
A Beta Minus Particle (B-)
-think that because a negative charge is being PRODUCED, the charge of the nucleus must increase (neutron -> proton)
What is the difference between B+ and B- decay?
When a B+ (Positron) is emitted the resulting nucleus will have a -1 atomic number
When a B- particle is emitted the resulting nucleus will have a +1 atomic number
When a proton decays into a neutron, what particle is emitted from the atom?
A Beta Plus Particle (Positron B+)
- think that because a positive charge was PRODUCED, the charge of the nucleus must decrease (proton -> neutron)
When an atom changes from a high energy to a low energy state what particle is emitted?
A Gamma Particle
What is the half-life of a radioactive sample?
The time it takes for half of that sample to decay
How do you multiply numbers in scientific notation?
- round the numbers to one decimal place and multiply them
2. add the exponents
What is a simpler way to solve for X^-2?
= 1/X^2
What is the square root of 121?
11
What is the square root of 196?
14
What is the square root of 256?
16
What is the square root of 289?
17
What is the square root of 361?
19
What is the Sin of a triangle?
Opposite/Hypontenuse
What is the Cos of a triangle?
Adjacent/Hypotenuse
What is the Tan of a triangle?
Opposite/Adjacent
What are the side lengths in a 30, 60, 90 triangle?
Side A = 1
Side B = sqrt 3
Hypotenuse = 2
What are the side lengths in a 45, 45, 90 triangle?
Side A = 1
Side B = 1
Hypotenuse = sqrt 2
What is the Sin of 0?
0
What is the Cos of 0?
1
What is the Tan of 0?
0
What is the prefix for 10^9 meters?
Giga (G) meters
What is the prefix for 10^6 grams?
Mega (M) grams
What is the prefix for 10^3 meters?
Kilo (k) meters
What is the prefix for 10^2 grams?
Hecto (h) grams
What is the prefix for 10^-1 meters?
Deci (d) meters
What is the prefix for 10^-2 grams
Centi (c) grams
What is the prefix for 10^-3 meters?
Milli (m) meters
What is the prefix for 10^-6 farads?
Micro (µ) farads
What is the prefix for 10^-9 meters?
Nano (n) meters
What is the prefix for 10^-12 grams?
Pico (p) grams
What is the difference between a positive and a negative control?
A positive control is a variable in an experiment that is maintained because it IS expected to have an effect on the dependent variable
A negative control is a variable that IS NOT expected to have an effect on the dependent variable
What type of experimental study would look at, over time, the different groups of people that have varying levels of risk factors?
A Cohort Study
What type of experimental study would attempt to break people into different groups at a specific point in time?
A Cross-Sectional Study
What type of experimental study would take a group of people with or without a particular outcome (such as cancer) and then seek to find the different groups exposure to risk factors (smoking)
A Case-Control Study
A scientist is trying to study how well a group of factory workers respond to positive rewards. However, he notices that even without doing anything, the group of factory workers increase their productivity because they know they are being observed. What is the name of this effect?
Hawthorne Effect
What type of variable can have an effect on both the dependent and independent variable?
Confounding variable
What is the difference between a parameter and a statistic?
Parameter- makes a claim about the entirety of a population using data (ex. all Wofford athletes are annoying)
Statistic- make a claim about a sample of a population (ex. Wofford athletes that are freshmen are annoying)
What is the mechanical advantage of a ramp?
The length of the ramp divided by its height
