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MCAT Comprehensive > Physics Review > Flashcards

Physics Review Flashcards

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1
Q

Define displacement, velocity, speed, and acceleration.

In what units are they measured?

A

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)

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2
Q

State each of the big five kinematic equations.

Under what conditions can they be applied?

A

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)

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3
Q

Give the magnitude and direction of free fall-acceleration near the surface of the earth

A

Direction of g is downward (10 m/s2) toward the surface of earth, radially toward the center

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4
Q

Define inertia. How is it measured? State Newton’s Law of Inertia

A

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

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5
Q

State Newton’s second Law of Motion.

Define Net force. In what units is it expressed?

A

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

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6
Q

State Newton’s third law of motion

A

If object exerts a force on object 2, then obect 2 exerts an equal and opposite force back on object 1.

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7
Q

Define weight.

Give at least two reasons why mass is different from weight

A

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

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8
Q

State Newton’s Law of Gravitation

A

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

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9
Q

Define normal force. Is the magnitude of the normal force on an object always equal to the objects weight?

A

FN is the component of the contact force exerted by a surface that is perpendicular to the surface.

No, it is not

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10
Q

Define friction and give the equation for the force of friction

A

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

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11
Q

Define center of mass. How is it located?

A

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)

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12
Q

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?

A

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

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13
Q

Give the equation for torque, lever arm, and rotational inertia

A

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

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14
Q

Define equilibrium

A

An object is in equilibrium if

Fnet=0 and tnet = 0

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15
Q

Define momentum. Is it a vector or scalar?

Define impulse. Is it a vector or scalar?

A

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

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16
Q

State the law of conservation of momentum

A

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

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17
Q

Define elastic collision, inelastic collision, and perfectly inelastic collision

A
  • 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

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18
Q

Define work and give its units

A

Work is the force acting over displacement

W = Fd cos (theta)

Scalar, measured in Joules

1 J = 1 N*m

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19
Q

Define power and give its units

A

Power = Work/time

Watts

1 W = 1 J/second

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20
Q

Define kinetic energy and give its units.

A

Kinetic energy is the energy an object has by virtue of its motion

½ m*v2

Joules

1 J = 1 N*M

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21
Q

Give the work energy theorem

A

Wtotal = Change in KE

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22
Q

Gravitational potential energy.

A

PEgrav = mgh

Delta h > 0 if going up

Delta h < o if going down

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23
Q

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?

A

E = KE + PE

KE1 + PE1 = KE2 + PE2

KEI + PEI + Wnc = KEf + PEf

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24
Q

Define heat and temperature. How are they different?

A

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

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25
Q
A

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

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26
Q

State the first Law of thermodynamics

Define internal energy and work

What are the sign conventions of heat and work?

A

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

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27
Q

Define isobaric, isochoric, isothermal, and adiabatic

A

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)

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28
Q

State the second law of thermodynamics. Define entropy

A

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)

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29
Q

Define stress and strain. What are their units?

How are they related?

A

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

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30
Q

Define density and specific gravity. What are their units?

What is the density of water?

A

Density = m/v

Specific gravity = psubstance/pwater

Density = kg/m3

Specific gravity has no units

pwater = 1,000 kg/m3 = 1 g/cm3

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31
Q

Buoyant force

A

Buoyant force = net upward force everted by a fluid

Fb = weight of fluid displaced = pfluid*Vsubmerged*g

32
Q

Pressure formula and units

A

Pressure = Force/Area

1 Pascal (Pa) = 1 N/m2

1 atm = 100 kPa or 105 Pa

33
Q

Gauge pressure and hydrostatic gauge pressure

A

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

34
Q

Define Pascals law

A

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

35
Q

Flow rate

Incompressible fluids

A

Flow rate f = Av (Cross-sectional area x flow speed)

M3/s

f1=f2 or A1v1 = A2v2

36
Q

Define ideal fluid flow

A

Ideal fluid flow occurs when the fluid is incompressible, has no viscosity, is laminar, and has a steady flow rate

37
Q

State Bernoulli’s equation and the conditions they may be applied

A

For ideal fluid flow

38
Q

What is the electric charge on a proton and electron?

A

e+/e- = +/- 1.6 x 10-19 C

39
Q

Equation for the electrostatic force between two point charges

A

Kqq/r2

k = 9 x 109 N*m2/C2

40
Q

Define conductor and insulator

A

Conductor = electric charges (free electrons) can move easily

Insulator = electric charges cannot move easily (rubber, wood, glass)

41
Q

Define electric field. How does the direction of the electric field depend on the sign of the source charge?

A

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

42
Q

Define electric potential and voltage and give their units

A

1 V = 1 J/C

43
Q

What is the relationship between electric field and electric force

A

The force on a charge at a position where the electric field is given by

F = qE

44
Q

Current units and how does it flow

A

Current (I) = net charge flowing per unit time in Amps

1 A = 1 C/s

Current flows in the direction of positive to negative

45
Q

Resistance

A

R = V/I

1 ohm = 1 V/A

R = pL/A

46
Q

Voltage

A

V = IR

R is independent of V or I

47
Q

Power lost by a resistor; what type of energy is this?

Power supplied by a voltage source; what type of energy is this?

A

P = I2R = IV = V2/R; thermal energy

P = IV; electrical energy

48
Q

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?

A

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.

49
Q

Define capacitor, capacitance, and dieletric. In what units is capacitance measured?

A

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

50
Q

How strong is the electric field between the plates of a capacitor? How much energy is stored? What is the effect of a dielectric?

A

E = V/d, d is the distance between the plates

PEelec = ½ CV2

A dielectric increases capacitance

51
Q

What generates a magnetic field? What are its units

A

A moving charge generated a magnetic field

B = Tesla

1 T = 1 (N*s)/C*m)

52
Q

Equation for the magnetic force exerted on a charge

What is the direction of this force?

A

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

53
Q

Define simple harmonic motion, amplitude, period, and frequency

What is the relationship between period and frequency?

A

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)

54
Q

Give the equation for the force exerted by and elastic potential energy stores in a stretched or compressed spring

A

F = -kx

PEelastic = ½kx2

55
Q

What determines the frequency of a spring-block simple harmonic oscillator?
Of a simple pendulum?

A

Mass of block and force constant of a spring

f = ½ (3) k/m

g and Length of a pendulum

½(3) g/L

56
Q

Define transverse wave and longitudinal wave

Define compression, and rarefaction

A

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

57
Q

What is the relationship between wave speed, wavelength, and frequency?

A

wave speed = frequency x wavelength

v = f*lambda

58
Q

What determines wave speed?

What determines the speed of a sound wave?

A

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

59
Q

What will happen to a wave’s frequency, speed, and wavelength when it enters a new medium?

A

Frequency remains unchanged

velocity and wavelength will change proportionately

60
Q

Define standing wave, node, antinode, harmonic frequency, and harmonic wavelength

A

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

61
Q

How do you calculate sound intensity and how is sound level calculated from sound intensity?

A

Sound intensity

I = Power/area

Sound level

B = 10 log (I/IO) where Io = 10-12 W/m2= threshold of hearing

62
Q

Describe the Doppler Effect. What conditions would result in increased observed frequency? Decreased observed frequency?

A

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

63
Q

Rank the colors of visible light in order from lowest to highest frequency

A

ROYGBV

64
Q

Define angle of incidence, angle of reflection, angle of refraction, and index of refraction

A

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

65
Q

Law of reflection and law of refraction

A

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)

66
Q

Define total internal reflection

When does it occur?

How do light and sound change when they pass through water?

Define diffraction

A

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.

67
Q

Equation for focal length

How do the terms concave and convex relate to converging and diverging lenses?

A

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

68
Q

Mirror lens equation

Magnification equation

A

1/o + 1/i = 1/f

m = -i/o

o = object distance from mirror or lens

i = image distance

69
Q

Real images and virtual images

A

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

70
Q

Lens power equation

Describe far-sightedness and nearsightedness

A

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

71
Q

Equation for the maximum kinetic energy of an electron ejected as a result of the photoelectric effect

Define work function and stopping potential

A

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

72
Q

Heisberg uncertainty relation

A

ΔxΔp≥ h/2π

The better one knows the position of a particle, the less one knows amount the momentum and vice versa

73
Q

Give the equation for stopping potential (Vstop)

A

KEmax = -eVstop

74
Q

What properties do light and sound waves share?

What can light do that sound cannot?

A

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

75
Q

Give Kirchoff’s Laws

A
  1. 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

  1. 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

MCAT Comprehensive (10 decks)

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