Equations - Paper 1 explained Flashcards
What is the equation for the first harmonic of a wave and what do all symbols mean?
f1 = (1/2L) * (T / u)½
L - length of the string (m)
T - Tension in the string (N)
u - Mass per unit length of the string (kg/m)
What is the formula for fringe spacing and what do the symbols mean?
w= λD/s
ONLY USE FOR DOUBLE SLIT
w - fringe spacing (m)
λ - wavelength of light (m)
D - distance between slits and the screen (m)
s - separation of slits (m) from centre to centre
What is the diffraction grating equation and what do the symbols mean?
dsinθ = nλ
d - distance between slits (m) - use unit/number
θ - the angle between the central and nth maxima (°)
n - maxima order number
λ - wavelength of the diffracted source (m)
What is the equation for phase difference between two points on a (progressive wave or stationary wave ask dan)?
φ = 2πd/λ = 360d/λ
φ - phase difference (degrees or radians)
d - horizontal distance between points (m)
λ - wavelength of the wave (m)
This isn’t on the formula sheet
What is the equation for the wavelength of the nth harmonic?
λn = λ1/n
λ1 - wavelenth of the first harmonic (m)
This isn’t on the formula sheet
What is the equation for the frequency of the nth harmonic?
fn = f1 * n
f1 - frequency of the first harmonic (Hz)
This isn’t on the formula sheet
What is the formula for the law of refraction?
n1sinθ1 = n2sinθ2
n - the refractive index of the medium
θ1 - angle of incidence
θ2 - angle of refraction
What is the equation for the number of maximums that can seen from a diffraction grating?
nmax = d/λ
Make sure to round down
d - speration of slits from centre to centre (m)
λ - wavelength of the wave (m)
This isn’t on the formula sheet
What is the formula for the work done on an object?
W = Fs
W - work done (J)
F - parallel component of force applied (N)
s - parallel component of displacement(m)
What is the equation for power in terms of energy and time?
P = ΔE/Δt
P - power (W)
E - energy transfered (J)
t - time (s)
What is the equation for power in terms of work done and time?
P = ΔW/Δt
P - power (W)
W - work done (J)
t - time (s)
What is difference about the v in kinetic energy compared to other formulas?
v in 1/2mv2 represents speed not velocity
Therefore, KE cannot be negative as it is a scalar just as speed is
What is the equation for power in terms of force and velocity?
P = Fv
Make sure to use driving force not resultant force
P - power (W)
F - driving force (F)
v - velocity (ms-1)
What are the two formulas for the energy stored in a spring?
E = 1/2FΔL
ΔL - extension of the spring (m)
F - force applied to the spring (N)
E = 1/2kΔL2
This one isn’t on the formula sheet
k - spring constant n/m
What is the formula for resistivity and what do the symbols mean?
p = RA / L
p - resistivity (Ωm)
R - resistance (Ω)
A - cross-sectional area of the wire (m2)
L - length of the wire (m)
What is the equation for work function in quantum?
φ = hf0
φ - work function (J)
H - Planck’s constant (Js)
f0 - threshold frequency (Hz)
This isn’t on the formula sheet
What is the equation for angular velocity in terms of θ and t?
ω = Δθ/Δt
ω - angular velocity (rads.s-1)
Δθ - angle the object has turned through (radians)
Δt - the time objects been turning (s)
What is the formula for the difference in frequency between energy levels?
E1 - E2 = hf
h - planck’s constant
f - frequency (Hz)
Can also sub in hc/λ if asked what wavelength of light will be emitted following a de-excitation between energy levels
What is the equation relating maximum kinetic energy and stopping potential in quantum?
KEmax = evs
KEmax - maximum ke of emited electrons (J)
e - magnitude of the charge of an electron
vs - stopping potential of a photoelectric circuit (V)
This isn’t on the formula sheet
What is the formula relating emf and energy in a circuit and what do the symbols mean?
ϵ = E / Q
ϵ - emf of the battery (V)
E - energy in the circuit (J)
Q - charge in the circuit (C)
From the definition, emf is the energy given to each unit of charge
What is the equation for angular velocity in terms of time period?
ω = 2π/Τ
ω - angular velocity (rads.s-1)
Τ - time period (s)
This isn’t on the formula sheet
What is the formula which links emf to V = IR?
ϵ = I(R + r)
r - internal resistance (Ω)
Total resistance is internal resistance + resistance in the circuit
Use for ‘imperfect’ circuits
What is the equation relating linear velocity and angular velocity?
ω = v/r
ω - angular velocity (rads.s-1)
r - radius of circular path (m)
v - linear velocity (ms-1)
What is the equation for the length of an arc of a circle?
s = rθ
s - arc length (m)
r - radius of the circle (m)
θ - angle of the arc (radians)
This isn’t on the formula sheet
When do you use x = Acos(wt) and x = Asin(wt)?
Use Acos(wt) when displacement is the amplitude when t = 0 (cos graph starts at max)
Use Asin(wt) when displacement is 0 when t = 0 (sin graph starts at 0)
This one isn’t on the formula sheet
MUST BE IN RADIANS
What is the equation relating max KE,PE and total energy in SHM?
KEmax = PEmax = Etotal = 1/2 mω2A2
m - mass of object that’s oscillating (kg)
ω - angular velocity of oscillations (rads.s-1)
A - amplitude of oscillations (m)
KEmax - maximum kinetic energy (J)
PEmax - maximum potential energy (J)
Etotal - maximum energy (J)
This isn’t on the formula sheet
What is the formula for the time period of a mass spring system and what do the symbols mean?
T = 2π (m/k)1/2
m - mass on the spring
k - spring constant
T - time period
What is the formula for the time period of a simple pendulum and what do the symbols mean?
T = 2π (l/g)1/2
l - length of the pendulum (m)
g - gravitational field strength (ms-2)
T - time period
When can you use P = FV?
When there is no acceleration, and force and velocity and parallel
