Physics Flashcards
Constant for coulombs law
K=9x10^9
Coulomb’s law/coulombs forces
F=(1/4piE)(q1q2/r^2) or F=k(q1q2/r^2) where k is a constant
q1/q2 is the charge on objects 1 and 2 respectively
Forces: attractive and repulsive forces btw charges
Force experienced by any charged particle located at x position in an electric field
F=k(q1q2/r^2) for total force Or F=Efs(q) Note: efs is in N/C - to get efs you must divide F by C -page 150-152
What is a capacitor? Electrostatic potential for a capacitor
- 2 plates of equal area, equal and opposite charge, and close to one another
V=Ed
E- electrostatic field strength
d- distance between plates
V- electrostatic potential in volts (J/C)
Note: the electrostatic force (coulomb’s force) changes if the charge is anything but 1 coulomb, changing the answer to J
What are the units for force?
Newtons (N)
1N = 1kgxm/s^2
Force is a vector quality
Units for energy/work
Joule (J)
1J = 1Nx1M
Energy and work are both scalar!
What are the units for power?
Watts (W)
1W=1J/s
Scalar
What are the units for charge?
Coulomb (C)
1C=1Axs
1A=6.2x10^18 electrons
What are the units for potential?
Volt (V)
1V=1J/C
What are the units for resistance?
Ohm
1ohm=1V/A
What are the units for capacitance?
Farad (F)
1F=1C/V
What are the units for magnetic field strength?
Tesla (T)
1T=1N/Axm
Formula for displacement, velocity, acceleration.
v=d/t
a=v/t
What is the formula for capacitance?
Capacitance=charge/electrostatic potential C=Q/V Expressed in Farad (F) 1F=C/V C=KEoA/d
Radians to degrees/degrees to radians
Degrees=radians x 180/pi
Radians=degrees x pi/180
Graph the sin, cosine, and tan graphs
See book
Special triangles
See book (p 23)
What is arcsine, arctan, etc
Question: What is arcsine 1? Arctan 1?
The inverse of sine, tan, etc
Answer: 90 degrees, 45 degrees
Arcsin 0.5 means sin x = 30 degrees
What is the square root of 3 and 2?
1.7 and 1.4 respectively
What are the “big 5” equations in uniformly accelerated motion?
- d = 1/2(Vi+Vf)t
- Vf = Vi + at
- d = Vit + 1/2at^2
- d = Vft - 1/2at^2
- Vf^2 = Vi^2 + 2ad
What are the proporionalities for kinematics where Vi = 0 and a is constant?
- Vf ~ t
- d ~ t^2
- Vf^2 ~ d
Solving in the x direction for projectile motion? Solving for y?
dx = Vox • t
For y use the big 5 as they apply.
In projectile motion, which way is velocity and acceleration?
Velocity is constant tangent to path of motion, and acceleration is downward.
The horizontal component of velocity remains constant.
Note a change in direction ALWAYS signifies acceleration
Formula for centripetal acceleration and centripetal force
a = v^2/r
Fc=mv^2/r
Note that real forces are needed to provide centripetal force!!!
Formula for velocity for centripetal acceleration
V = d/t
V = 2piR/T
T being period
Newtons second law.
Fnet = ma Fnet = F1 + F2 + ...
Newtons third law
F (2 on 1) = -F (1 on 2) m1a1 = m2a2 Note that force exists even if the object isn't accelerating See p 65 for action reaction pair Also see question on page 66
Newton’s universal law of gravitation
Fg = G (m1m2/r^2)
G is the universal gravitational constant
How do you rearrange the gravitational equation to get gravity on any given planet?
g = Gm(earth)/R^2(earth) Fg = mg mg = G (m1m2/R^2)
What is the equation for kinetic and static friction?
Ff,k = UkFn
Ff,s <= UsFn
Us is always large than Uk! Both are unit less
Kinetic friction always opposes the objects motion and static opposes the intended motion
Once the object is moving the value of kinetic friction remains constant regardless of whether the applied force changes
See p 76/78/82 question
What is the value of tan theta?
What is the value of arctan 1?
Tan theta = sin theta/cos theta
45 degrees
What is the formula for centripetal force?
Fc = ma(centripetal) = m • v^2/r
See p 83 question
Formula for finding the center of mass?
Xcm = m1x1 + m2x2 + … / m1 + m2 + …
What is the formula for torque? What are its units? Scalar or vector? When is it maxamizd/minimized Lever arm formula?
T = rFsin€ or T = l • F In N•m NOT jewels!! Vector Maximized at 90 degrees, minimized at 0 or 180 T=l•F -> l is lever arm
Formula for work and it’s units
Direction?
W = Fdcos€ or W = Fd Measured in jewels (J) = N•m Scalar Minimized at 90 degrees (0 work) Page 99
What are the formulas for total work? Work done by changing forces? Work-kinetic energy theorem? Total work done by gravity?
Wtotal = W1 + W2 + ... (W on the object) You can do this because work is Scalar so it can just be added W-k energy theorem: Wt = []Ek (without vectors) p 101 If done by gravity Wt = []Ek and Wt=Wg=[]Ep therefore []Ek = -[]Ep
What is the formula for work done by gravity?
Wg = mgh
Formula/definition for kinetic energy
Ek = 1/2mv^2
In jewels
-the energy inherent in the movement of an object
Formula for potential energy
Ep = mgh
In jewels
Conservation of mechanical energy formulae
E = Ek + Ep -[]Ep = []Ek Eki + Epi = Ekf + Epf -the energy of an isolate system is constant -see note on page 108!
Formula for conservation of mechanical energy when a non-conservative force is involved (any force apart from gravity, spring force, and electrostatic force)
Eki + Epi + Wf = Ekf + Epf
Or
Wf = [] (Ek + Ep)
-see p 108
What is the formula for power as its units?
P=W/[]t or W/t In watts (W) = J/s P = Fvcos€ = N•m/s - for a constant force - see p 111
What is the formula for linear momentum? Scalar or vector?
p = mv
In kg•m/s
Vector quantity
What is the formula for impulse?
Conservation of linear momentum
m1v1i + m2v2i = m1v1f + m2v2f
Elastic vs inelastic collision vs perfectly inelasic
Both - pi = pf
Elastic collision - Eki = Ekf
Inelastic collision - Eki =/= Ekf (objects will gain Ek if they start together then separate)
Perfectly inelastic collisions are when objects stick together and Eki>Ekf (loses Ek)
Ek1i + Ek2i = Ek1f + Ek2f
Units for density/formula and density of water
Density = mass/volume
Kg/m^2
1000 kg/m^2
Specific gravity formula
Density of solid/density of water
Unit-less
Density of water is 1000kg/m^2
Units for a pascal (Pa)
1Pa = 1N/m^2
Tensile stress formula
Tss = F/A
A is cross sectional area
Units - pascal (Pa) (N/m^3)
Tensile strain formula
[]L/Li
Unit-less
Young’s modulus
Tensile stress/tensile strain In pascals (Pa) -substance/object must obey hookes law to use this formula (anything that does not will not be tested on the Mcat)
Fluid pressure formula (gauge pressure)
P=p(g)(h)
p is fluid density
h is height of fluid above point in question
Fluid pressure formula (absolute pressure)
P=p(g)(h) + atmospheric pressure
For real situations
Buoyancy force formula (Archimedes principal)
Fb=Vpg or weight of fluid displaced
In Newtons
Volume of fluid displaced•density of fluid displaced•gravity
See p 132 question
Formula/units for flow
Flow(Q) = volume/time Q=(area of pipe)(velocity of fluid) In m^3/s This is for ideal (laminar) flow -look at p 133/134 for rules of ideal flow/turbulent flow -flow is equal at all points in a vessel
Caliber
Width of the vessel
Recall: flow(Q)=area•velocity
Decreased caliber = decreased pressure and increased flow (velocity)
Caliber and pressure are not proportional (an increase in one does cause increase in the other and vice versa though)
How to calculate work/energy for parallel plate capacitors
Work = Efs • d
In jewels
Page 162-164
- know that capacitors do store energy and the energy storage is related to the electrical potential difference btw plates
Define the dielectrics breaking point
The Efs at which discharge occurs (electrons move from negative to positive plate)
Ohms law
I = V/R I current (A) V voltage (V) R resistance (ohm) -note this applies when 2 entities of different potential are connected by a conductor
Formula for current
I = Q/t
Coulombs per second
Equations for power in electric circuits
P=IV P=I^2R P=V^2/R In watt (W) -> work/time (J/s) - you can also describe it as N•m/s
How to sum resistors connected in series
Rt = R1+R2+….
In ohms
How to sum resistors connected in parallel
1/Rt = 1/R1 + 1/R2 + …
In ohms
-note the total resistance will always be smaller than the smallest resistor in parallel
How to calculate the voltage drop over the course of an electric circuit
Use equation V=IR
V is voltage drop between any 2 points in the circuit
I is circuits current (constant throughout)
R is resistance btw the 2 points
Note: all voltage drops added together should equal total voltage
Describe magnetic field strength wrt current running through a wire
Strength is inversely proportional to distance from the wire and has direction
Measured in Telsa (T = N/A•m)
Dot means current it flowing to you, x means into page
Right hand rules (pg 191)
Formula for the force exerted on a charged particle moving through a magnetic field
F = qvB q is charge of the force v is velocity of particle B is magnetic field strength Direction is determined by other right hand rule (p 191)
What is a cycle and a period and frequency? For transverse and longitudinal waves
Cycle = one rotation (trough crest trough or for transverse waves, areas of rarefaction compression rarefaction)
period = time it takes to complete one cycle (in seconds)
Frequency = cycles/second (in hertz H)
-note that frequency is the reciprocal of period (if you know one you know the other)
What is wavelength?
Distance from one point to the next identical point on a wave measured in meters/cycle (lambda) or just meters.
How to measure the speed of a wave
V=frequency•wavelength
- in m/s
What factors affect the speed of a sound wave?
Resistance to compression is directly proportional to speed and density of the medium is inversely proportional to speed.
Note that sound is a longitudinal compression wave
How to measure loudness ad intensity
Loudness = decibels (dB) Intensity = watts per square meter
What is the threshold of human hearing?
10^-12 watts per square meter
The equation that relates loudness and intensity
Loudness = 10log(I/Io)
Io = threshold oh human hearing = 10^-12W/m^2
Note page 207 for shortcut (100 x intensity = 20 + loudness)
The Doppler effect
fo = fs (v+-vo/v+-vs)
vo is + if observer moves toward source and - if away
vs is - if source moves toward observer and + if away
Hooke’s law
F=-k(x)
k is spring constant (in N/m)
x is distance from point of maximum velocity
- force is weight of pendulum or tension within the spring
K for a pendulum is ~weight of pendulum over length of pendulum (k is given for springs)
- hookes law may only be applied if the object is said to obey hookes law (or is called a hookes law spring)
Spring constant wrt a pendulum
k=weight of pendulum/length of pendulum
Speed of light
3x10^8 m/s
Refractive index
Refractive index of a medium = speed of light in a vacuum/speed of light in the medium
- is the degree to which the travel of light is slowed through a medium
- dimensionless
- index of refraction varies slightly with the frequency that transverses it
Snell’s law
Used for refraction
n1sin€1=n2sin€2
Formula for the critical angle
sin€cr = nb/na
Focal length of a mirror
f=1/2Rc
Rc is radius of curvature
f is - for convex and + for concave
Thin lense equation
1/f = 1/o + 1/i
o is distance of object from mirror
i is distance of image from mirror
Mirror image location-real/virtual-orientation-sign
For mirrors
location-r/v-orientation-sign
Convex: Behind - v - upright - (-)
Concave: In front - r - inverted - (+)*
*objects placed within focal distance will create a virtual, upright image
Mirror magnification equation
m = -i/o
i is distance of image from mirror
o is distance of object from mirror
Note: - magnification indicates inverted image
Lens makers equation (for lenses)
1/f = (n-1)(1/R1-1/R2)
R is radius of curvature for sides 1 and 2
Know whether f and R are + or -
(pg 233)
Type-image-focal point for lenses
Type-image-focal point
Diverging - front,v, upright - front(-)
Converg. - beh.,r,inv - behind (+)*
*objects placed within focal distance will create virtual upright image
Magnification and thin lense equation for lenses
Same as for mirrors
m=-i/o
1/f=1/o+1/i
Focal power
The degree to which a lens imposes convergence or divergence on the light rays that traverse it
P=1/f
Expressed in diopters
- f is in METERS!
Note: + and - signs matter since we are using f (- for diverging and + for converging)
Calories to jewel conversion
1 cal = 4.18 J
J to eV conversion
eV to J
1J= 6.24x10^18 eV 1eV= 1.6x10^-19 J
atm to N/m^2 (Pa)
atm to torr (mmHg)
1atm = 1.013x10^5 Pa 1atm = 760 torr (mmHg)
Coefficient of static friction
Us=tan(theta)
Explain translational and rotational equilibrium
Translational - net force is 0
Rotational - net torque is 0
What is spring potential energy?
E=kx^2/2
Name the conservative forces
Gravity, spring force, electrostatic force
Page 102
Units for an ampere
Coulomb’s/second
1A = 1c/s
What is an electron volt?
Unit of energy (J) equal to the work done on an electron (in accelerating it through a potential difference of one volt)
How many joules are in a megajoule?
A million (1,000,000)
Formula for circumference of a circle/area. How many radians in a circle?
2pi(r) = circumference
Pi(r)^2 = area
2(pi) radians in a circle or 6.28
How do you estimate small (<15 degree) angles?
Sin theta = theta
Tan theta = theta
Cos theta = 1
Newton’s first law
Inertia - an object initially at rest or in motion with a constant velocity will remain in its initial state unless acted upon by a nonzero net external force (an object tends not to accelerate)
Describe the direction of net force and velocity relationship
Page 64
What is weight v mass
Mass = intrinsic property of an object (kg) Weight = force (mass times acceleration)
What is the normal force/tension?
The force that the surface exerts on the object
It is always perpendicular to the surface
Tension is always a pulling force on the Mcat
Describe rotational inertia
Page 87
Describe the 4 useful facts about work
P 100
What is the mechanical advantage?
Increase in displacement and decrease in force required to do THE SAME amount of work
-work does not change
Describe the impact of padded vs hard surfaces on force
Also, how to calculate impulse from a graph
P 114
What happens with momentum in recoil and explosion problems? Collisions in 2d?
Page 118
Describe pascals principle for fluid pressure
Fluid pressure at any given depth in a resting fluid is unrelated to the shape of the container
How do you determine whether an object sinks or floats?
See what is greater, the force of the weight of the object (down) or buoyancy force (up)
Define electron mobility, electrical conductors, insulators, and contact charge
P 141-143
Know what will produce/experience a contact charge
Explain induction (and how it’s different from contact charge)
Page 145-146
Formula for electric field strength (capacitors)
Efs=Q/(eo)(A) units in N/C Q: magnitude of charge on either plate eo: permittivity constant A: area of either plate OR efs = V/d (distance) - from V=Ed
What are the equations for a capacitors energy?
u=1/2QV
u=1/2CV^2
u=Q^2/2C
What is the electromotive force? Internal resistance?
The potential difference that promotes the flow of current
Measured in volts (not newtons)
It moves electrons from positive back to the negative terminal (they flow naturally from negative to positive)
Without the emf, electrons would not flow
-current flow it often called the flow of positive charge (even though + do not move)
- if a battery source had internal resistance, V (across battery) = emf - IR (voltage drop of internal resistance)
Describe the naming of batteries/conductors
A 2 volt battery means the cathode and anode differ in electrical potential by 2 volts
- every conductor even as it mediates the flow of current simultaneously resists it
- note all conductors are resistors and vice versa
Describe current in a series circuit/parallel circuit
Series: I1 = I2 = I3
Parallel: I1 + I2 + I3
Describe voltage in parallel and series circuits
Parallel: V1 = V2 = V3
Series: V1 + V2 + V3
Define pitch, infrasonic and ultrasonic
Pitch is how high or low a sound is and is synonymous with frequency ( measured in Hz)
The human hearing range is between 10 and 20,000 Hz (below 10 is infrasonic and above is ultrasonic)
What is a restorative force? (For oscillation)
A force that tends to restore the moving object to the point at which it has no potential energy (opposite to velocity)
Describe the conservation of energy wrt harmonic motion
Total sum of kinetic and potential energy must be constant throughout
What is the frequency for light equation?
f = speed/wavelength f = 3x10^8/wavelength
Define visible light, white light, infrared, and ultraviolet
Visible light = electromagnetic radiation that is normally conceived of as a wave
- in the field of optics it is depicted as a ray
P 219
Define reflection and refraction. What is the angle of incidence and angle of refraction/reflection?
P 221
When does total internal reflection occur?
When a ray of light travels trough a medium and encounters a second medium with lower index of refraction than the first
- it is when the ray reflects instead of refracts
What are converging/diverging lenses associated with?
Convexity and concavity respectively
Formula for resistance of a wire
Resistance = resistivity • (length/area)
Which way will light bend when contacting a second medium?
If index of refraction (n) is >1 towards vertical point of intersection line (bc light moves slower)
If n is < 1 away from the poi line
