Physics Review Flashcards
Define displacement, velocity, speed, and acceleration.
In what units are they measured?
Displacement is the change in position (magnitude = net distance or distance from start to finish) in meters
Velocity is the rate of change of position = Change in position/ change in time
Speed is the magnitude of velocity (m/s)
Acceleration is the change in velocity over change in time (m/s2)
State each of the big five kinematic equations.
Under what conditions can they be applied?
d = ½ (vo + v)
v = vo + at
v = vot + ½ at2
vo = vt - ½ at2
v2 = vo2 + 2ad
They can only be applied when acceleration is constant (uniform)
Give the magnitude and direction of free fall-acceleration near the surface of the earth
Direction of g is downward (10 m/s2) toward the surface of earth, radially toward the center
Define inertia. How is it measured? State Newton’s Law of Inertia
Inertia is an object’s natural resistance to change in its state of motion.
It is measured by mass in kg
Fnet = 0 when velocity is constant
State Newton’s second Law of Motion.
Define Net force. In what units is it expressed?
Fnet = ma
where the net force = the sum of all forces acting on the object
Force is measured in Newtons
1 N = 1 kg*m/s2
State Newton’s third law of motion
If object exerts a force on object 2, then obect 2 exerts an equal and opposite force back on object 1.
Define weight.
Give at least two reasons why mass is different from weight
Weight is the gravitational force acting on an object. It varies with location and is measured in Newtons.
Mass is not a force and does not vary with location (eg. on Eath vs on the moon) and is measured in kg
State Newton’s Law of Gravitation
Every pair of objects exerts a gravitational attraction on each other and its strength
F = GMm/r2,
Where G = is the universal gravitational constant (6.6 x 10-11 m3/kg*s2)
r is the center of mass to center of mass
Define normal force. Is the magnitude of the normal force on an object always equal to the objects weight?
FN is the component of the contact force exerted by a surface that is perpendicular to the surface.
No, it is not
Define friction and give the equation for the force of friction
friction is the component of the contact force exerted by a surface that is parallel to the surface
fk = uk* FN
fs(max) = us* FN
Define center of mass. How is it located?
The point where all object’s mass can be considered to be concentrated = point that behaves as if the object were a single particle = the balance point.
xcm= (m1x1 + m2x2)/(m1*m2)
Define uniform circular motion, centripetal acceleration, and centripetal force
Give the formulas of the magnitudes of centripetal acceleration and centripetal force.
What are their directions?
UCM = constant-speed motion in a circle
ac= acceleration toward the center of a circle necessary to keep an object on a circular path without changing its speed.
ac= v2/r
Fc = the net force necessary to cause centripetal acceleration
Fc = ma = mv2/r
Both point toward the center of the circle
Give the equation for torque, lever arm, and rotational inertia
t = rFsin(theta) = I*F
tnet = Ia
Where I is the rotational inertia
The farther the mass is from the axis of rotation, the larger the rotational inertia
Arms tucked in = less resistance to turning = lower rotational intertia
Define equilibrium
An object is in equilibrium if
Fnet=0 and tnet = 0
Define momentum. Is it a vector or scalar?
Define impulse. Is it a vector or scalar?
Linear momentum = mass x velocity
p = mv in kg*m/s
Impulse = force x change in time
J = F*t
Impulse and momentum are both fectors
State the law of conservation of momentum
If not net external force acts, then total momentum is conserved in a collision between freely moving objects
Total pbefore = total pafter
Since momentum is a vector, it is conserved in all directions
Define elastic collision, inelastic collision, and perfectly inelastic collision
- Elastic collision* is when objects bounce off one another without deforming; kinetic energy is conserved
- Inelastic collision* involves deformation of the object; kinetic energy is not conserved
Momentum is conserved in both elastic and inelastic collisions*
Perfectly inelastic is when objects stick together after the collision
A perfectly elastic collision the greatest kinetic energy loss in a collision, as not only do they deform, they form a single object
Set the total momentum equal to the total mass times velocity
ptotal = mtotal x v
Define work and give its units
Work is the force acting over displacement
W = Fd cos (theta)
Scalar, measured in Joules
1 J = 1 N*m
Define power and give its units
Power = Work/time
Watts
1 W = 1 J/second
Define kinetic energy and give its units.
Kinetic energy is the energy an object has by virtue of its motion
½ m*v2
Joules
1 J = 1 N*M
Give the work energy theorem
Wtotal = Change in KE
Gravitational potential energy.
PEgrav = mgh
Delta h > 0 if going up
Delta h < o if going down
What is the equation for total mechanical energy? and the law of mechanical conservation of energy?
What is the work done by non-conservative forces?
E = KE + PE
KE1 + PE1 = KE2 + PE2
KEI + PEI + Wnc = KEf + PEf
Define heat and temperature. How are they different?
Heat is the transfer of thermal (internal) energy between a system and its environment. An extensive property - depends on the mass of the material
Temperature is a measure of the average kinetic energy of molecules in a system. An intensive property - doesn’t depend on the amount of material
Conduction is heat transferred through contact
Convection is heat transferred by moving masses of fluid
Radiation is heat transferred by emission and absorption of electromagnetic waves or photons
State the first Law of thermodynamics
Define internal energy and work
What are the sign conventions of heat and work?
Change in Energy E = Q - W
Q = net heat transfer, W = net work
Change in internal energy of a system depends on how much heat is transferred into or out of the system and the work done by or on the system
W is the work done by the system.
If the gas expands, W is positive. (System does positive work)
If gas is compressed, W is negative (Work is done on the system)
If heat is added to the system, Q is positive
If heat is removed from the system, Q is negative
Define isobaric, isochoric, isothermal, and adiabatic
Isobaric = constant pressure W = Q - PΔV
Isochoric = constant volume ΔE = Q
- Isochoric processes do no work, all of the energy change is due to heat flow (Piston is locked in place with a stopper)
Isothermal = constant temperature Q = W
- (Ideal gas in a metal cylinder submerged in a water bath)
Adiabatic = no heat is exchanged between the system and the environment ΔE = -W (insulated cylinder)
State the second law of thermodynamics. Define entropy
Entropy of a closed system stays the same or increases during any thermodynamic process (Heat cannot be completely converted to work)
Entropy is a measure of the disorder of a system
Increase in entropy (+ΔS)
Decrease in entropy (-ΔS)
Define stress and strain. What are their units?
How are they related?
Stress = Force/Area
Tensile or compressive stress, force is perpendicular to area
Shear stress, force is parallel to area
Stress = N/m2
Strain = ΔL/L (change in length over original length)
Strain has no units
Stress is proportional to strain
Define density and specific gravity. What are their units?
What is the density of water?
Density = m/v
Specific gravity = psubstance/pwater
Density = kg/m3
Specific gravity has no units
pwater = 1,000 kg/m3 = 1 g/cm3
Buoyant force
Buoyant force = net upward force everted by a fluid
Fb = weight of fluid displaced = pfluid*Vsubmerged*g
Pressure formula and units
Pressure = Force/Area
1 Pascal (Pa) = 1 N/m2
1 atm = 100 kPa or 105 Pa
Gauge pressure and hydrostatic gauge pressure
Gauge pressure = Total pressure - atmospheric pressure
Ptotal = Psurface + Pgauge
Hydrostatic gauge pressure is the pressure due to being immersed within a fluid (depends only on depth)
P = pfluid*g*d
d = depth
Define Pascals law
A pressure that is applied to the surface of a confined liquid is transmitted undiminished to every part of the fluid; all points have the same height and same pressure
Flow rate
Incompressible fluids
Flow rate f = Av (Cross-sectional area x flow speed)
M3/s
f1=f2 or A1v1 = A2v2
Define ideal fluid flow
Ideal fluid flow occurs when the fluid is incompressible, has no viscosity, is laminar, and has a steady flow rate
State Bernoulli’s equation and the conditions they may be applied
For ideal fluid flow
What is the electric charge on a proton and electron?
e+/e- = +/- 1.6 x 10-19 C
Equation for the electrostatic force between two point charges
Kqq/r2
k = 9 x 109 N*m2/C2
Define conductor and insulator
Conductor = electric charges (free electrons) can move easily
Insulator = electric charges cannot move easily (rubber, wood, glass)
Define electric field. How does the direction of the electric field depend on the sign of the source charge?
Electric field = electric force per unit charge
Field lines point away from positive charges and toward negative charges
Electric field strength:
E = kQ/r2
E = N/C or V/m
Define electric potential and voltage and give their units
1 V = 1 J/C
What is the relationship between electric field and electric force
The force on a charge at a position where the electric field is given by
F = qE
Current units and how does it flow
Current (I) = net charge flowing per unit time in Amps
1 A = 1 C/s
Current flows in the direction of positive to negative
Resistance
R = V/I
1 ohm = 1 V/A
R = pL/A
Voltage
V = IR
R is independent of V or I
Power lost by a resistor; what type of energy is this?
Power supplied by a voltage source; what type of energy is this?
P = I2R = IV = V2/R; thermal energy
P = IV; electrical energy
What does an ammeter measure? Where should it be placed in a circuit? What is its ideal resistance?
What does a voltmeter measure? Where should it be placed in a circuit? What is its ideal resistance?
How are photoelectrons detected? Where do they travel?
An ammeter measures current and should be placed in series with the compenent it is measuring. Its ideal resistance is 0.
A voltmeter measures voltage and should be placed in parallel with the component whose voltage it is measuring. Its ideal resistance is infinite.
Photoelectrons are detected by the ammeter, and wants to go to areas of higher potential, as they are electrons.
Define capacitor, capacitance, and dieletric. In what units is capacitance measured?
Capacitor = two conductors (usually parallel plates) carrying equal but opposite charges
Capacitance = charge/voltage C = Q/V
C is in farads
1 F = 1 C/V
Dielectric is an insulator between capacitor plates
How strong is the electric field between the plates of a capacitor? How much energy is stored? What is the effect of a dielectric?
E = V/d, d is the distance between the plates
PEelec = ½ CV2
A dielectric increases capacitance
What generates a magnetic field? What are its units
A moving charge generated a magnetic field
B = Tesla
1 T = 1 (N*s)/C*m)
Equation for the magnetic force exerted on a charge
What is the direction of this force?
F = q(v x B)
Magnitude of force: F = qvBsin(theta)
Force is perpendivular to velocity
B obeys right hand rule
- point thumb in the direction of the velocity
* = out of the plane/ x = into the plane
Fingers point in the direction of the field (B)
Palm points in the direction of Fb for positive charge / back of hand is for negative charge
Force is always perpendicular to velocity and the field
Define simple harmonic motion, amplitude, period, and frequency
What is the relationship between period and frequency?
SHM = Oscillatory motion, where restoring force is proportional to displacement
Amplitude is the maximum displacement from equilibrium
Period = time required for the oscillator to complete one full cycle
frequency = # cycles per unit time
f = 1/T
Spring frequency; f = 1/2(pi) x (sq(k/m)
Give the equation for the force exerted by and elastic potential energy stores in a stretched or compressed spring
F = -kx
PEelastic = ½kx2
What determines the frequency of a spring-block simple harmonic oscillator?
Of a simple pendulum?
Mass of block and force constant of a spring
f = ½ (3) k/m
g and Length of a pendulum
½(3) g/L
Define transverse wave and longitudinal wave
Define compression, and rarefaction
Transverse wave: oscillation of medium is perpendicular to the propagation of the wave (sound waves/light)
Longitudinal wave - motion of medium is parallel to the propagation of the wave
Compression = the region of maximum pressure
Rarefaction = the region of minimum pressure
What is the relationship between wave speed, wavelength, and frequency?
wave speed = frequency x wavelength
v = f*lambda
What determines wave speed?
What determines the speed of a sound wave?
Properties of the medium (except when taking into account dispersion with light, where frequency matters to a small extent)
Speed of sound is determined by the medium’s resistance to compression
v = (B/p)½
What will happen to a wave’s frequency, speed, and wavelength when it enters a new medium?
Frequency remains unchanged
velocity and wavelength will change proportionately
Define standing wave, node, antinode, harmonic frequency, and harmonic wavelength
Standing wave = superposition of two oppositely-directed traveling waves that results in a single, non-traveling wave
Node = point of zero displacement
antinode = point of maximum displacement
Harmonic frequency = common frequency of traveling waves that will produce a standing wave
Harmonic wavelength = common. wavelength of traveling waves that will produce a standing wave
How do you calculate sound intensity and how is sound level calculated from sound intensity?
Sound intensity
I = Power/area
Sound level
B = 10 log (I/IO) where Io = 10-12 W/m2= threshold of hearing
Describe the Doppler Effect. What conditions would result in increased observed frequency? Decreased observed frequency?
The change in the observed frequency of an acoustive wave caused by relative motion of the source and detector
Relative motion toward results in higher observed frequency
Motion away results in a lower observed frequency
Rank the colors of visible light in order from lowest to highest frequency
ROYGBV
Define angle of incidence, angle of reflection, angle of refraction, and index of refraction
Angleincidence = angle that the incident beam makes with the normal boundary
Anglereflect = angle that the reflected beam makes with normal to boundary
Index of refraction:
n = c / v
v = speed of light through the medium under study
Law of reflection and law of refraction
Law of reflection is for mirrors:
Angle of incidence = angle of reflection
Law of refraction (Snell’s Law) if for lenses:
n1*sin(theta) = n2*sin(theta)
Define total internal reflection
When does it occur?
How do light and sound change when they pass through water?
Define diffraction
Total internal reflection occurs when the light strikes the boundary of a medium with a lower refractive index (n2 < n1) at an angle of incidence greater than the critical angle
Light going from water to air
Sin thetacritical = (n2/n1)
Light gets slower in water, bending toward from the normal
Sound gets faster in water, bending away from the normal
Diffraction is the spreading out of waves when they encounter an obstacle or aperature.
Equation for focal length
How do the terms concave and convex relate to converging and diverging lenses?
Focal length: f = r/2
Virtual images form from diverging optics (concave lens/convex mirror) - i < 0, f > 0, m > 0 and the image is upright
Real images form from converging optics (convex lens/concave mirror) - i < 0, f < 0, m < 0 and the image is inverted
Mirror lens equation
Magnification equation
1/o + 1/i = 1/f
m = -i/o
o = object distance from mirror or lens
i = image distance
Real images and virtual images
Real image is formed by the actual convergence of light rays
Real images are always inverted
Virtual image is an image from which light only appears to diverge
Virtual images are always upright
Lens power equation
Describe far-sightedness and nearsightedness
P = 1/f
Hyperopia - far-sightedness
Focal length of the lens system is too long, image forms behind the retina (Use a converging lens to fix)
Myopia - near-sightedness; can see things that are close
Focal length of the eye’s lens system is too short, image forms in front of the retina (Use a diverging lens to fix)
If not using a lens to fix; Strength of the eye lens (Which is a converging lens) is positive
Equation for the maximum kinetic energy of an electron ejected as a result of the photoelectric effect
Define work function and stopping potential
KEmax = hf - f = -eVstop
Work function f is the minimum energy needed to dislodge a surface electron from a metal
Stopping potential is the minimum voltage required to prevent ejected electrons from reaching the detecer
Heisberg uncertainty relation
ΔxΔp≥ h/2π
The better one knows the position of a particle, the less one knows amount the momentum and vice versa
Give the equation for stopping potential (Vstop)
KEmax = -eVstop
What properties do light and sound waves share?
What can light do that sound cannot?
They both can reflect, refract, and diffract. They both have a speed of propagation (v = frequency * wavelength)
Light can be polarized
Light can propagate without a medium, meaning that it can travel in a vacuum
Give Kirchoff’s Laws
- Conjunction rule - currents into and out of any point in a circuit must equal each other. (Conservation of charge)
Elements in series have equal current
I1 = I2 + I3
- Loop rule - sum of voltages arond any closed loop circuit must equal zero. (Conservation of energy)
Elements in parallel have the same voltage
+Vbattery + (-V1) + (-V2) = 0
