Physics Quicksheets Flashcards
Current equation
I=Q/T in amperes(C/s)
Emf
Electromotive force - “pressure to move” or the difference in potential (voltage) between 2 terminals
Kirchoffs junction rule
I into the junction = I leaving the junction
Kirchhoffs loop rule
For a closed circuit loop, sum of the voltage sources=sum of voltage(potential) drops cuz conservation of energy!
vectors
physical quantities with both magnitude and direction (force, velocity)
scalars
physical quantities with magnitude no direction (mass, speed)
Displacement
change in position that goes in a straight-line path from the initial position to the final position, independent of the path taken
average velocity
x/t (m/s)
acceleration
rate of change of an object’s velocity v/t (m/s^2)
kinematic equations
projectile motion - vertical component =
-horizontal component =
= v sin theta
= v cos theta
static friction (and equation)
force must be overcome to set an object in motion
kinetic friction (and equation)
opposes motion of objects moving relative to each other
Newton’s first law
law of inertia - body in a state of motion or at rest will remain in that state unless acted upon by a net force
Newton’s second law
when a net force is applied to a body of mass m, the body will be accelerated in the same direction as the force applied to the mass
F=ma (N or kgm/s^2)
If a person in a hot air balloon is falling downwards and the F(gravity) > F(drag) then
person is accelerating downward
If a person in a hot air balloon is falling downward and the F(gravity) = F(drag) then
person is traveling at constant velocity
Newton’s third law
If body A exerts a force on body B, then B will exert a force back onto A that is equal in magnitude, but opposite in direction
Fb = - Fa
Newton’s law of gravitation (equation)
all forms of matter experience an attractive force to other forms of matter in the universe
mass vs weight
mass - scalar, measures inertia
weight - vector, measures body’s gravitational attraction to the earth (Fg = mg)
first condition of equilibrium
an object is in translational equilibrium when the sum of forces pushing it one direction is counterbalanced by the sum of forces acting in the opposite direction
sum F =0
Work
constant force acting on an object that moves a displacement of d
W=Fdcos(theta) in Nm
For a force perpendicular to displacement, W=?
0
For an expanding piston, if W>0
work is done by the system
When a piston compresses a gas, W<0 means
work is done on the system
How to determine work from a P vs V curve?
area under the curve
power
rate at which work is performed
P = W/t in J/s
energy is vector/scalar
scalar in J
kinetic energy equation
1/2 mv^2
Potential energy
energy associated with a body’s position, gravitational potential energy due to gravity acting on an object
U = mgh
Total mechanical energy equation
When is it conserved?
E= U + K
when sum of kinetic and potential energies remains constant
Work-energy theorem
relates work performed by all forces acting on a body in a particular time interval to the change in energy at that time
net W = change in energy
Conservation of energy
when there are no nonconservative forces (like friction) acting on a system, the total mechanical energy re,ains constant
change in E = change in K + change in U = 0
linear expansion (mnemonic)
increase in length by most solids when heated
when temperature increases, the length of a solid increases “a Lot”
volume expansion
increase in volume of fluids with heated
conduction
convection
radiation
direct transfer of energy via molecular collisions
transfer of energy by the physical motion of a fluid
transfer of energy by electromagnetic waves
specific heat (Q)
Q=mc/\T for object does not change phase
Q>0
heat gained
Q<0
heat lost
heat of transformation
quantity of heat required to change the phase of 1 g of a substance
Q =mL
phase changes are ________ processes
isothermal
first law of thermodynamics
/\U = Q - W
for an adiabatic process, the first law of thermodynamics becomes
/\U=-W
for a constant volume process, the first law of thermodynamics becomes
/\U = Q
for an isothermal process, the first law of thermodynamics becomes
Q=W
second law of thermodynamics
in any thermodynamic process that moves from 1 state of equilibrium to another, the entropy of the system and environment together will either increase or remain unchanged
density
m/v in kg/m^3
specific gravity
density of substance/density of water
density of water
10^3 kg/m^3
weight of a fluid
=density*gV
pressure
=F/A in pascals or N/m^2
for static fluids of uniform density in a sealed vessel, pressure =
density*gravity*z
z=depth of the object
absolute pressure
in a fluid due to gravity somewhere below the surface
P = P(initial) + density*gz
gauge pressure
P(gauge) = P - Patm
where P = P(initial) - pgz
when P(initial) = Patm then P(gauge) = pgz
continuity equation
A1V1 = A2V2
bernoulli’s equation
P + 1/2 pv^2 + pgh
buoyant force equation
Fb = density of fluid * g* Vsubmerged
archimedes principle
buoyant force is equal to the weight of the displaced fluid.
if the weight of the fluid displaced is less than the object’s weight, the object will sink
if the weight of the fluid displaced is greater than or equal to the object’s weight, then it will float
Pascal’s principle
change in pressure applied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the containing vessel
coulomb’s law
like charges repel and opposite charges attract, with a force proportional to the product of the charges and inversely proportional to the square of the distance between them.
electric field
positive point change will move in the same direction as the electric field vector
negative charge will move in the opposite direction
electrical potential energy
for a charge q at a point in space its the amount of work required to move it from infinity to that point
U = q*/\V = qEd = (kQq)/r
in J
Electric potential
amount of work required to move a positive test charge q from infinity to a particular point divided by the test charge
V=U/q in J/C
direction of current
direction that positive charge would flow, from high to low potential
ohm’s law
V=IR
resistance
opposition to the flow of charge
when temperature increases, resistance
increases
power dissipated by resistors (3 equations)
P=IV=V^2/R=I^2*R
capacitance
ability to store charge per unit voltage
C=Q/V
