Equations Flashcards
Doppler Effect
Transverse waves
particle oscillation is perpendicular to the direction of propogation and energy transfer.
Example: light waves
Longitudional waves
particle oscillation is parallel to the direction of propogation and energy transfer
Example: sound
Think slinky
speed of wave
v = f lambda
Period of wave
T = 1/f
seconds per cycle
one cycle = one wavelength = 360 degrees
Intensity of sound
Intensity: power/energy per unit area
I = Power/Area
I is proportional to amplitude^2
I is proportional to 1/distance^2
Vector components
X = V cos angle
Y = V sin angle
Coulomb’s law
the electrostatic force between two charges
Electric field
Every electric charge sets up a surrounding electric field
E = F/q
E = kQ/r^2
F = the force between the charges
Q = charge that creates the field (source charge)
q = the charge placed in the field (test charge)
r = distance between them
*Coulomb’s divided by q (obviously b/c of first eqn)
Electric Potential Energy
The work necessary to move a charge in an electric field
U = kQq/r
q = charge that is being moved
Q = charge that is creating electric field (source charge)
*Coulomb’s times r
Electric Potential
electric potential = voltage
V = kQ/r
Kinetic energy
1/2 mv^2
Potential energy
U = mgh
Elastic Potential Energy
1/2 kx^2
Work
W = F d cos angle
W = (Change V) P
Work-energy
The net work done by forces acting on an object will result in a chnage in the KE
Wnet = K final - K initial
Power
P = W/t = change Energy/ time
Watt = J/s
Electrical Power
P =IV
Pressure
P = F/A
or F = AP
Absolute (hydrostatic) Pressure
P = P(surface) + p (density) g z (depth of object)
P(surface) could be atmospheric pressure
Hydraulic Systems
V = A1 d1 = A2 d2
W = F1 d1 = F2 d2
Buoyancy Force
F = p(denisty fluid) V(fluid displaced) g
F = p(densiy fluid) V(submerged) g
If floating, F buoy = F gravity
Flow rate
Flow rate is constant in a tube regardless of cross-sectional area
Q (flow rate) = A1 v1 = A2 v2
v = linear speed (which does change)
Bernoulli’s eqn
density of water
1000 kg/m^3
Resistance
R = p(resistivity) L(length of resistor)/A (area)
longer length = more resistance
larger cross-sectional area = less resistance
Ohm’s law
V = IR
Resistors in series
Rtot = R1 + R2 +…
Current is same throughout each resistor
Vtot = V1 + V2 +…
Resistors in parallel
1/Rtot = 1/R1 + 1/R2 +…
Current splits at each branch in circuit
I tot = I1 + I2 +…
Voltage is the same through each resistor
V tot = V1 = V2 =…
Sound level
B = 10 log(I/10^-12)
I = intensity of sound wave (I = P/A)
10^-12 is threshold of hearing
String
antinodes = # harmonics = n
lambda = 2L/n
Open Pipe
of nodes = harmonic # = n
lambda = 2L/n
Closed pipe
quarter-wavelengths (quarter circle) = harmonic # = n
lambda = 4L/n
Electromagnetic spectrum increasing frequency
Radio Waves –> microwave –> IR –> red –> purple –> UV –> X rays –> gamma rays
Energy of wave
E = hf = hc/lambda
Visible region
violet (400nm) –> red (700nm)
