Physics Flashcards
Gravitation
- Law of universal universal gravitation is
- Gravitational field g =
- Gravitational potential energy Ug =
- Gravitational force F = G m1 m2 / r2
- g = G m / r2
- Ug = - G m1m2 / r
Lenz’s law
The polarity of the induced emf ………………..
The polarity of the induced emf is such that the induced current
creates a magnetic field that tends to oppose the change that produced it
Capacitance
C =
C = Q / V
Potential energy
- describe in words
- Gravity - formula general
- Gravity - formula Earths gravity
- Two charges interacting by Electric force - formula
- In a stretched spring - formula
- The energy of position
- Ug = -G m1 m2 /r
- U = mgh
- Ue = k q1 q2 /r
- Uspr = 1/2 k x2
Electrostatic potential energy between two point charges U =
Electrostatic potential energy between two point charges
U = kq1q2/r
Sound waves
loudness in decibels =
Sound Intensity with distance
Planar waves =
Cylindrical waves =
Spherical waves =
loudness in decibels = 10 log10 (I / Io) Intensity , Io is 10-12 W/m2
Planar waves I = constant
Cylindrical waves I = 1/r
Spherical waves I = 1/r2
Archimedes principle
formula in words
Buoyant force = weight of fluid displaced
Heat engine
- What is the maximum amount of work you can get out of a heat engine =
- What are the implications of The Second Law of Thermodynamics for efficiency of machines?
- The maximum amount of work you can get out of a heat engine is the amount you get out of a reversible engine.
Wmax = (Qhigh - Qlow)reversible
= Qhigh - QhighTlow/Thigh = Qhigh(1 - Tlow/Thigh).
- No 100% efficiency <em>(a heat engine exhaust gas would have to be 0 Kelvin which is impossible)</em>
The Second Law of Thermodynamics states that the state of entropy of the entire universe, as an isolated system, will always increase over time.
The second law has been expressed in many ways.
Pascal’s law
formula
leads to hyd….. …ess
Fa/Aa = Fb/Ab
hydraulic press
Mass-spring
- ..?.. Law
- Restoring force =
- Angular frequency =
- ..?.. potential energy = 4a
- Hooke’s law
- F = -k x spring constant displacement
- w = (k/m)1/2
-
Elastic potential energy
4a. U = 1/2 k x2
Wave superposition
standing waves fixed at both ends, wavelength =
standing waves fixed at one end e.g tube, wavelength =
standing waves fixed at both ends
wavelengthn = 2L / n (n = 1,2,3,4,5…)
standing waves fixed at one end e.g tube, wavelength =
wavelengthn = 4L / n (n = 1,,3,,5…)
Electricity
- Coulomb’s law force between two point charges F =
- Define electric field E =
2a. and in words - Electric field around a point charge E =
- F = kq1q2/r2
- E = F/q
2a. Electric field predicts the force that would exert on a test charge - Electric field around a point charge E = kq/r2
Wave propogation
- speed of wave on a stretched string =
- and for a harmonic wave =
- v = (F / u)1/2 Tension / mu is mass per unit length
- v = lambda x f
Simple harmonic motion
Displacement =
Frequency = =
Period =
x = A cos (ωt + δ)
displacement = max displacement cos( angular velocity x time + phase angle)
f = 1/T = ω/2π
T = 2π/ω
Transmission of heat
- Rate of heat flow (by conduction) =
- Rate of heat flow (by radiation) =
1. Q/t = K A (deltaT/deltax)
K is thermal conductivity of the material
deltax is conductor thickness
- Stefan’s law
Q/t = A epsilon sigma T4
epsilon is emissivity
sigma is Stefan-Boltzmann constant
Newton’s laws of motion
Number
title
formula
1st Law - The law of Inertia
If net force = 0 then acceleration = 0
2nd Law - Net force causes acceleration
F = ma
3rd Law - Action and reaction
F12 = F21
Sources of the magnetic field
- Magnetic field on a straight current carrying wire B =
- Magnetic field at the centre of a current loop B =
- Magnetic field within a solenoid B =
- Magnetic field on a straight current carrying wire
B = μ0 I /( 2 π d) [μ0 = permeability of free space; I=current, d=distance from wire]
- Magnetic field at the centre of a current loop[radius r]
B = μ0 I / (2r)
- Magnetic field within a solenoid[n turns per unit length]
B = n μ0 I
Faraday’s law
The emf induced by a changing magnetic flux through a circuit is
………
directly proportional to the time rate of change of the magnetic flux through the circuit
What is the photoelectric effect?
Relate wavelength of light to frequency
λ = c / f
Doppler effect
f’ =
Rotational kinematics (3 of 3)
- Angular momentum of a body - formula
- Angular momentum of a particle moving around a point - formula
- L = I w
- L = p r sintheta momentum of particle rho x radius x sin..
or more formally by the vector product L = r x p
- additional - The direction is given by the right hand rule which would give L the direction out of the diagram. For an orbit, angular momentum isconserved, and this leads to one ofKepler’s laws. For a circular orbit, L becomes L = mvr
Magnetic force
- Magnetic force on a segment of current carrying conductor F =
- Torque on a current loop within a uniform magnetic field T =
- F = L I B sin θ
[L=segment length, I=current, θ= angle between current and magnetic field]
- T = I A B cos Φ
[A=area of loop, Φ = angle between loop plane and magnetic field]
Rotational kinematics (2 of 3)
- Rotational kinetic energy - formula
- Rotational Work - formula
- Rotational Power - formula
- K = 1/2 I w2 moment of inertia angular velocity omega
- W = T x deltatheta Work = Torque x angular displacement
- P = Tw Power = Torque x angular velocity
Kinetic energy
formula
K = 1/2 m v2
Momentum - formula
Conservation of momentum - formula
Impulse = =
Collisions - types & formulae
p = m v
sum of initial momentum = sum of final momentum
Impulse = F deltat = deltap
Elastic collision (billiard ball) -> momentum conserved; kinetic energy conserved
Inelastic collision (putty) -> m1 v1 + m1 v2 = (m1 + m2) vf
Electrical generators and motors
- How does a generator work?
- How does a motor work?
- Generator
Mechanical work -> changes magnetic flux -> induces emf
- Motor
Electical energy -> changes magnetic flux -> mechanical work
Work
define in words
formula
Work = force x component of displacement in the direction of the force
W = (F cos theta) s
Rotational kinematics (1 of 3)
- rotating object change in angular displacement - formula & units
- Torque - formula (words and symbols)
- Moment of inertia - formula & when greater
- relate torque and angular acceleration
- theta = arclength / radius radians
- Torque = F d force x movement arm
- I = sum mi ri2 greater when mass further from axis of rotation
- Torque = moment of inertia x angular acceleration
Wave propogation
velocity of sound formula
v = (B / p)1/2 Bulk modulus / rho is density
Fluid mechanics
- density =
- pressure =
- pressure at depth h =
- p = m/V
- P = F/A
- P = atmospheric pressure + pgh
Geometric optics - mirrors
- focal length of concave and convex mirrors - formula
- magnitude of lateral magnification M =
- 1/f = 1/di + 1/do
- M = - di/do = hi/ho
Conservation of energy
formula
Utotal = initial (K + U) = final (K + U)
Power
- Definition
- formula
- Power in terms of force - formula
- Rate of energy expenditure OR work done
- P = Work/t
- P = F v
Four equations of kinematics
one dimension
uniform acceleration
s = v0t + 1/2 at2
s = 1/2(v + v0)t
v = v0 + at
v2 = v02 + 2as
Wave superposition
beat frequency =
fb = f1 - f2
Systems and surroundings
Define types of systems and what can and cannot be transferred to the surroundings
what and can be transferred to the surroundings
Open - matter and energy
Closed - energy
Isolated - nothing
Flow of an ideal fluid
….. flux formula
Ber…….. law formula
volume flux
A1V1 = A2V2
Bernouilli’s law
P + 1/2pv2 + pgy = constant
Pressure + Kinetic energy + Potential energy = constant
Electricity
Gauss’s law
Gauss’s law -
Flux through a closed surface = net enclosed electric charge / permittivity of free space
Elasticity
- elastic modulus =
- ..?.. deformation 2a. Young’s modulus =
- shear modulus =
- bulk modulus =
- elastic modulus = stress / strain
- tensile deformation 2a. Young’s modulus = (F/A) / (deltaL/L0)
- shear modulus = (F/A) / (deltax/h)
- bulk modulus = (F/A) / (deltaV/V)
The Pendulum
Angular frequency =
w = (g / L)1/2
PV work
- explain
- formula
- draw PV graph
Magnetic force
- Force on a particle with velocity perpendicular to a magnetic field F =
- A particle moving perpendicular to a magnetic field experiences centripital magnetic force leading to uniform circular motion F =
- F = q v B sin θ [= q(v X B) vector cross]
- F = qvB = mv2/r [sin = 1, solve for r]
Angular momentum
- in terms of mass and velocity L =
- In terms of linear momentum L =
- In terms of angular velocity L =
L = m v r (v is tangential to r)
L = ρ r (ρ is tangential to r)
L = m ω r2
Friction forces
Types
Formulae
Static friction
Fsmaximum = usN (coefficient of static friction mus, Normal force)
Kinetic friction
Fk = ukN (coefficient of kinetic friction muk, Normal force)
Electric potential - voltage
- Define voltage in words
1a. V = - two points in space near a test charge V =
- between parallel charged plates V =
- Voltage is the work a field can do on a test charge
1a. V = ΔU / q W/A J/C - two points in space near a test charge V = kq [1/ra - 1/rb]
- between parallel charged plates V = Ed
Geometric optics
What is Michel van Biezel method for finding where the image is for mirrors and lenses?
- Draw a horizontal line from the top of the object to the surface and then through the focal point
- Draw a line from the top of the object through the focal point
Continue the lines, where they cross is the top of the object - shows position and inversion
Thermal expansion
Linear =
Area =
Volume =
deltal = a lo deltaT alpha is coefficient of linear expansion
deltaA = 2a Ao deltaT
deltaV = 3a Vo deltaT
Black body
what is the emissivity of a perfect black body radiator? ε =
ε = 1
Classical fundamental forces
How many
Names
Formulae
Gravitational force F = G m1 m2 / r2
Electrostatic force F = k q1 q2 / r2
Magnetic force F = q B v sin theta
Inductance
How do inductors work?
On switch on it takes time for current to reach maximum.
The back emf initially opposes the applied voltage
Heat engine
- Diagramatically represent a heat engine
- What is the work you get out of a heat engine =
SI derived units
Name, units, what it is for : eg kg = kilogram, kg, mass
N
Pa
J
W
C
F
V
Heat capacity
Define specific heat
Define Molar heat
Specific heat c Q = m c deltaT c joules per gram to raise 1o Kelvin
Molar heat capacity C Q = n C deltaT C joules per mol to raise 1o Kelvin
Kepler’s laws of planetary motion
Name and describe in words
Kepler’s laws of planetary motion are three scientific laws describing the motion of planets around the Sun
First law - the Orbital rule
The orbit of a planet is an ellipse with the Sun at one of the two foci.
Second law - the Area rule
A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
Third law - the Period rule
The square of the orbital period of a planet is proportional to the cube of the semi-major axis of its orbit.
acceleration in uniform circular motion
formula
name
direction
a = v2 / r
Centripital acceleration
to centre
