Physics Flashcards
What is a Newton equal?
kg * m/s2
What is a Pascal equal to?
F/A
N/m2
Conversion of Pascal to atm
1 atm = 1*10^5 Pa
What is a Joule equal to?
N*m
What is a Watt equal to?
J/s
Conversion of ºC to Kelvin?
K = ºC + 273
sin(0)
0
cos(0)
1
sin(90)
1
cos(90)
0
sin(30)
0.5
cos(30)
0.9
cos(45)
0.7
sin(60)
0.9
Specific heat formula
Q=mc∆T
How many liters are in one mol of gas?
22.4
Standard work formula
W = F•d•cos(theta)
Work on gases at constant pressure
W = P•∆V
How do ramps give a mechanical advantage?
increase the distance, so decrease the amount of force needed to input
F1D1 = F2D2 W1 = W2
Mechanical advantage of inclined plane formula
incline length / incline height
d in / d out
Power formula
P = work / t
What are units for power?
J/s or Watts
What are the units for work?
N * m, J
Torque formula
T = Fdsin(theta)
Spring force
F = -kx
Centripetal acceleration formula
a = (Vt)^2 / r
What is the units of energy?
joules
PE elastic
= 1/2 kx^2
Positive work
work done on an object by its environment
increases an object’s kinetic energy
Negative work
work done on the environment by an object
decreases an object’s kinetic energy
As velocity increases what happens to air resistance?
it increases
What happens at terminal velocity?
Fg = Far
there is no net force
In projectile motion what is time dependent on?
the vertical motion only
Temperature
a measure of hotness that is proportional to the kinetic energy of the object
heat
energy transferred between two substances of different temperatures
Thermal equilibrium
temperature is the same
What velocity do you have to use for the kinetic energy of a particle?
Vrms
What is the body temperature in ºC?
37ºC
What is the body temp in K?
~300K
What is boiling point of water in ºC?
100ºC
What is the absolute zero?
0K
What does absolute zero mean?
there is no vibration between atoms
What is heat measured in?
joules
Conduction
heat transfer by direct contact between substances
Convection
focuses on circulation of liquids and gases
Radiation
energy transferred between electromagnetic waves
What types of expansion can happen from heat?
length and volume
As gases expand, what happens to work?
they do work on the environment and they lose energy
As gases contract, what happens to work?
the environment does work on the gas and gases increase in energy
First law of thermodynamics
energy cannot be created or destroyed
Energy of a closed system
∆U = Q - Work by system
Second law of thermodynamics
entropy will increase over time
Relationship between entropy and heat
∆S = Q/T
more heat transferred = more entropy
What makes heat transfers spontaneous?
entropy
Coulomb unit
Ampere * seconds
What is the magnitude of charge for protons and electrons?
1.6 * 10^-19
Electric field units
N/C
What is Fe in an electric field?
F = qE
What is work done by an electric field?
W=q∆V
W = kQq / r
If we move a positive charge in the direction of the electric field, do we do positive or negative work?
the potential energy decreases, so the kinetic energy increases
more kinetic energy, means we added energy and did positive work
Diamagnetic
fully paired orbitals
cannot generate a magnetic field
Paramagnetic
unpaired electrons have no net spin and material as a whole has no dipole
How can a paramagnetic material form a dipole?
if another magnetic field is brought close
Ferromagnetic
unpaired electrons retain a stable, non-random distribution of spin
permanent magnets
What direction do magnetic field lines go?
from North to South pole on outside of bar magnet
What does current physically refer to?
the movement of positive charges
At what angle is there no net magnetic force?
when the particle is moving parallel to the magnetic field
When does the magnetic field produce uniform circular motion?
when the magnetic field is completely perpendicular to the charge
Formula for acceleration in uniform circular motion
a = v^2/r
Formula for radius of uniform circular motion from magnetic field
r = mv/qB
Formula for magnetic field generated from a current
B = uI / 2pi*r
What is current equivalent to conceptually?
charge / time
DC current
current moves in a single direction through the circuit
AC current
direction of current changes
Formula for resistance of wire
R = p(length / area)
Voltage
the difference in electric potential between two points
Dielectric material
in-between the plates of a parallel capacitor
Capacitor formula
Q = VC
What does capacitance refer to?
how well the capacitor can store charge
Capacitance formula
C = kEA/d
What does greater dielectric material mean?
means greater capacitance (can hold more charge on the plates)
What is the formula for the electric field between the parallel plate?
E = V/d
What is the formula for the potential energy stored in a capacitor?
PE = 1/2CV^2
What direction does the electric field inside the capacitor point?
from + to -
the same direction that electric field lines point
Formula for period for spring
T = 2pi*sqrt(m/k)
Formula for period of pendulum
T = 2pi*sqrt(L/g)
What are the two types of mechanical waves?
transverse and longitudinal
transverse waves
move forward horizontally from particles moving vertically
example of a transverse wave
stadium wave
people stand up and wave moves forward
longitudinal waves
move back and forth on same axis that waves propagate
particles bunch and spread
What is an example of longitudinal wave?
sound
Standing wave
made of multiple waves combining
resonance frequency
object’s natural vibration frequency enabling max amplitude
wavelength formula for standing wave with closed ends
wavelength = 2L/n
n= harmonic number
wavelength formula for closed pipe
wavelength = 4L/n
n= odd harmonic number
closed pipe
refers to pipe only being closed at one end
for fixed strings, what does the harmonic number tell?
the number of antinodees
for open strings, what does the harmonic number tell?
the number of nodes
What are equivalent units for density?
g/mL, g/cm3, and kg/L
What is the density of water?
1 g/mL
What does specific gravity equal?
the density of the liquid
What is 1 atm equal to?
10^5 Pa or 760 mmHg
Hydrostatic pressure
Psub = pgh
p= density of fluid
absolute pressure
hydrostatic pressure + atmospheric pressure
gauge pressure
system pressure - atmospheric pressure
% submerged
object’s density/liquid’s density *100
Buoyant force
pVg
V= volume of fluid displaced p = density of fluid
Pascal’s law
a change in pressure at any point in an enclosed fluid at rest is transmitted to all points in the fluid
F1/A1 = F2/A2
Why do system’s want to minimize surface tension?
more surface tension = more energy
What is true of submerged fluids at equilibrium?
the buoyant force equals the gravitational force
What are the units for viscosity?
Pa*s
Relationship between viscosity and temperature
Viscosity decreases with increasing temp
Laminar flow
flowing fluid is composed of parallel layers that may be moving at different velocities
Turbulent flow
flowing fluid composed of mixed layers that vary dramatically in pressure and speed
Reynolds number
higher Reynolds number indicates higher turbulent flow
Poiseuille’s law definition
used to describe laminar flow of incompressible fluids through a long cylindrical tube, with no change in fluid height
Relationship between pressure drop and flow rate
Increase in pressure drop leads to an increase in flow rate
Bernoulli’s law
applies potential energy to fluids
When can Bernoulli’s law be applied?
assume laminar flow
neglect viscosity
neglect interactions between the fluid and the container
What do the terms in Bernoulli’s law tell us?
1) pressure exerted against the container walls
2) kinetic energy
3) gravitational potential energy
If a container is open on one end, what is pressure equal to?
the atmospheric pressure
What is true of the flow rate within a closed system?
The flow rate is constant
Is velocity the same as flow rate?
No!
At a constant height, increasing velocity will?
decrease pressure
Pressure in capillaries
Capillaries have large total surface area which decreases velocity but not flow rate
When velocity decreases, pressure increases
Venturi effect
when area decreases, velocity increases
when velocity increases, pressure decreases
Strong nuclear force
holds protons together in nucleus
overcomes the repulsive electromagnetic force
Mass defect
occurs from binding energy of nucleus forming
some particle’s mass becomes energy
nucleus has smaller mass than predicted
What does E=mc^2 refer to?
the binding energy
m= mass defect amount
What are the units of binding energy?
eV
What is the energy of a photon?
E = hf
Photoelectric effect
when photons hit metal, they excite electrons in the material, causing electron emission
What is the energy of an emitted electron?
E = hf - work function
Work function
the minimum amount of energy a photon must have to release an electron
Nuclear fusion
neutrons are force together, releasing a ton of energy through binding energy
Alpha decay
an alpha particle with 2 protons and 2 neutrons is released (Helium nucleus)
What changes in the parent nucleus after alpha decay?
decreases by 2 in atomic number and by 4 in mass number
Beta-minus decay
neutron converted to proton and a B- electron is emitted
atomic number increase by one
Beta-plus decay
proton converted to neutron and B+/positron is emitted
atomic number decreases by one
Positron
released during Beta-plus decay
the mass equivalent of an electron but with opposite charge
Electron capture
a reaction where an electron is absorbed and merged with a proton which forms a neutron
atomic number decreases by one
Gamma decay
emission of a high energy photon
Why is gamma decay not light emission?
it involves exciting a neutron not an electron
light wavelength is much shorter than visible light
Half-life formula
Nt = No (1/2)^(t/t 0.5)
What to be careful of in half-life calculations?
determining amount remaining versus amount decayed
Through what type of medium does sound travel the fastest? Why?
sound travels the fastest through a solid medium due to a large Bulk modulus
Through what type of medium does sound travel the slowest? Why?
sound travels the slowest through a gas medium due to a small Bulk modulus
Bulk modulus
a material’s resistance to compression
What is the speed of sound in air?
340 m/s
Ex: how much more intense is 50dB than 30dB?
100 times more intense
When is Vo positive in Doppler effect?
if the observer is moving towards the source
causes higher frequency
When is Vs positive in Doppler effect?
if the source is moving away from the observer
causes lower frequency
Doppler effect formula
Fo = Fs(v+vo / v+vs)
Does blue or red light bend more towards the normal?
blue light
shorter wavelengths bend more towards the normal
When is the critical angle experienced?
when the refractive angle is 90º and we are moving from a higher to a lower n
Dispersion
colors spread out since higher wavelengths bend more than lower wavelengths
What is the focal length for a concave mirror?
positive
What is the focal length for a convex mirror?
negative
What is the focal length for a concave lens?
negative
What is another name for a concave lens?
diverging
What is the focal length for a convex/converging lens?
positive
Myopia
another name for nearsightedness
How do you correct nearsightedness?
with a diverging lens
