MCAT Physics Comprehensive

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MCAT Physics Comprehensive
2012-08-02 19:23:04

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  1. Average velocity
    Vavg = (V1 + V2) / 2
  2. Determining height reached
    Time to reach peak * average velocity
  3. Determining horizontal distance
    Total time in air * X component of Vinitial
  4. Net force = 0 means...
    No acceleration. Can however have velocity but a = 0
  5. If volume changes, is work being done?
  6. Tension is...
  7. Vector attributes
    Has both magnitude and direction.
  8. Scalar attributes
    Has only magnitude
  9. Newton's first law
    The velocity of a body remains constant unless the body is acted upon by an external force.
  10. Newton's second law
  11. Newton's third law
    For every action there is an equal and opposite reaction.
  12. Inertia definition
    The ability of an object to resist a change to its velocity.
  13. Center of Mass formula
    Cmass = (r1m1 + r2m2 + r3m3...)/mtotal

    r - the displacement vector between a reference point and each vector.
  14. Center of gravity
    At the center of mass.
  15. Center of buoyancy
    The geometric center, irrespective of the center of mass.
  16. "Constant Velocity" or " Constant Speed" means
    • No acceleration
    • No NET force
    • All forces sum to zero
    • No change in direction
    • The object is in equilibrium
  17. Distance or height traveled formula
    Distance = rate * time
  18. Range (horizontal distance traveled) formula
    Range = Vx * time
  19. When facing projectiles think:
    • Horizontal velocity never changes (ignoring wind resistance)
    • Horizontal acceleration always = 0
    • Vertical acceleration always = 10 m/s2
    • Vertical behavior is always symmetrical (upward = downward)
    • Time in the air depends on the vertical component of velocity only.
    • Range depends on both the vertical and horizontal components.
    • Time is always the same for both the x and y components of the motion.
  20. Formula for displacement in projectile motion
    X = 1/2at2
  21. Formula for final velocity when only height is given
    V = √(2gh)
  22. Formula for "round trip" or total time in air
    tair = 2V/g

    V must be the vertical component of initial velocity
  23. The effect of surface area on air resistance
    Greater surface area = more air resistance
  24. The effect of shape on air resistance
    Less aerodynamic = more air resistance
  25. The effect of contour on air resistance
    Rough surface = more air resistance
  26. The effect of velocity on air resistance
    Greater velocity = more air resistance
  27. Gravity definition
    A field that exists between any two objects with mass.
  28. Field definition
    An invisible influence that can exert a force on a mass or charge.
  29. Universal Law of Gravitation (force due to gravity)

    (In space)

    F = mg

    (Near earth)
  30. Formula for gravity, strength of gravitational field, acceleration due to gravity
  31. Gravitational Potential Energy

    (In space)

    PE = mgh

    (Near earth)
  32. Friction facts
    • Friction opposes sliding not motion.
    • If there is sliding, it's kinetic friction; if there's no sliding, it's static friction.
    • Static µ is always greater than kinetic µ.
    • Surface area does not increase friction when the mass is the same.
  33. Force due to friction formula
    Ff = µ(s/k)FN

    Ff = µ(s/k)mgcos
  34. Force down an inclined plane formula
    F = mgsin
  35. Normal force on an inclined plane formula
    FN = mgcos
  36. Velocity at the base of an inclined plane
    Vf = √(2gh)
  37. Hooke's Law
    F = k∆x

    • x - displacement
    • k - spring constant
  38. Elastic Potential Energy formula
  39. Simple Harmonic Motion formulas
    T = 2π√(m/k)

    (mass on a spring)

    T = 2π√(L/g)


    • T - period (time/wave)
    • m - mass
    • k - spring constant
    • L - length of pendulum
    • g - gravity
  40. Equililbrium terms
    • Terminal velocity
    • Constant velocity
    • Objects at rest
    • Balanced fulcrums or boards on strings
    • Objects floating in liquid
  41. Torque and lever arms
    • T = F
    • T = mg
    • T = Frsin

    • - lever arm
    • r - distance between the force and the point of rotation.
    • rsin - always equals , but r = only when = 90˚
  42. Solving for systems in and not in equilibrium
    Equilibrium - list all the forces and put them equal to one another.

    Not Equilibrium - list all the forces and add "ma" to the loosing side.
  43. Circular motion formula
  44. Centripetal vs. Centrifugal
    If a string is pulling a ball into a circular motion, the string's force on the ball is centripetal and the ball's force on the string is centrifugal.

    Centrifugal does not exist.
  45. Angular motion formulas

    • - angular frequency (rad/s)
    • v - tangential velocity (m/s)
    • r - radius (m)
    • f - frequency (Hz)

    For the MCAT angular frequency and angular velocity are synonymous.
  46. Rotational equilibrium
    • An object is in rotational equilibrium if:
    • 1. It is NOT rotataing
    • 2. It is rotating with a constant angular velocity/frequency
  47. Momentum

    momentum is inertia increased by velocity and is always conserved (remains constant) in an isolated system.
  48. Impulse
    • Impulse = ∆
    • Impulse = m∆v
    • Impulse = Favgt

    • If there is no change in velocity, there can be no impulse.
    • The greater the change in velocity the greater the change in impulse.
  49. Elastic Collisions
    • (KE1 + KE2)before + (KE1 + KE2)after
    • In elastic collisions momentum and energy are both conserved.
  50. Inelastic Collisions
    m1v1 + m2v2 = m1v1 + m2v2

    In inelastic collisions momentum is conserved but energy is not. For perfectly inelastic collisions the equations becomes:

    m1v1 + m2v2 = (m1 + m2)v3
  51. Stress
  52. Strain
    ∆dimension/original dimension
  53. Modulus of elasticity (ME)

    • Young's modulus - simultaneous pushing or pulling, perfectly lined up with one another.
    • Shear modulus - simultaneous pushing or pulling not perfectly lined up.
    • Bulk modulus - simultaneous compression from all sides.
  54. Thermal expansion formula
    ∆L = Lo∆T

    • T - temperature
    • L - length in inches
    • - coefficient of thermal expansion
  55. Internal energy
    The energy of internal vibrations of molecules or atoms within a system.
  56. Heat energy
    Energy dissipated as heat. On the MCAT this usually means heat dissipated from a collision.

    Heat energy and internal energy are almost synonymous.
  57. Chemical energy
    The energy contained within chemical bonds, or the energy stored/released due to the separation and/or flow of electrons.
  58. Mechanical energy
    ME = KE + PE
  59. Work formulas
    • W = ∆Energy
    • W = Fdcos

    Units - Joules () or ()
  60. Atmospheric Pressure
    Force per unit area exerted upon a surface by the weight of the air above that surface in the atmosphere.
  61. Fluid Pressure
    Force exerted by a fluid on a point equal to the density of the fluid times the depth.
  62. Gauge Pressure
    The pressure difference between a system and the surrounding atmosphere.
  63. 1 atm equivalents
    • 760 torr
    • 760 mmHg
    • 101 kPa
    • 101,000 Pa
    • 14.7 psi
  64. General Pressure formula
    P = F/A

    Pressure = Force / Area
  65. Fluid Pressure formula
    P = gh

    • (rho) = fluid density
    • g = gravity
    • h = height of fluid
  66. Specific Gravity formula
    SG = Dsubstance/DH2O

    D = density
  67. Density of water
    • 1000 kg/m3
    • 1.0 g/cm3
  68. Volume measurements of water
    1cm3 = 1mL
  69. Mass of water
    1L = 1kg

    1mL = 1gram
  70. For objects floating in fluid, the fraction submerged =
    The ratio of the density of the object to the density of the liquid.
  71. Archimede's Principle
    The buoyant force is exactly equal to the weight of the displaced fluid.
  72. Buoyancy formula
    Fbuoyant = vg

    • = fluid density
    • v = volume of displaced fluid
    • g = gravity
  73. Apparent Weight
    The apparent weight of a submerged object is the actual weight minus the buoyant force.

    The apparent weight gives us 1) the buoyant force and 2) the weight of that volume of fluid.
  74. Flow Rate formula
    • Q = AV
    • Q = flow
    • A = cross-sectional area of tube (m2)
    • V = velocity of the fluid (m/s)

    Application (cardiac output = stroke volume x heart rate)
  75. Bernoulli's Equation
    K = P + gh + 1/2 v2

    • P = random kinetic energy of the fluid molecules
    • gh = the gravitational potential energy of the fluid
    • 1/2v2 = the energy due to moving fluid molecules
    • K = a constant
  76. Velocity of H2O exiting a spigot formula
    v = √(2gh)
  77. Surface Tension
    The intensity of intermolecular forces per unit length at the surface of a liquid.
  78. Adhesion
    An attraction between unlike particles.
  79. Cohesion
    An attraction between particles of the same kind.
  80. Charge magnitude of an electron
    e- = 1.6 E-19 C
  81. Current flows...
    From positive (+) to negative (–)
  82. Electrons flow...
    From negative (–) to positive (+)
  83. What is current?
    The flow of eletrons from areas of higher density (where they strongly repel each other) to areas of lower density (where there is less repulsion).
  84. Electric Field
    Field = an invisible influence that can exert a force on a mass or charge.
  85. Point Charge Field
    Equates to "real" gravity or gravity in space.
  86. Constant Electric Field
    Equate to "assumed" gravity or gravity near earth.
  87. Electric field equivalent to "g" gravity
    E - Strength of electric field
  88. Electric field equivalent to "G" gravity constant
    K - constant
  89. Electric field equivalent to "h" height
    r - radius or distance
  90. Electric field equivalent to "m" inertial component
    q - charge
  91. Strength of an e-field formula
    E = V/d

    • E - strength of an electric field
    • V - voltage
    • d - distance
  92. Voltage for point charge e-field formula
    V = Kq/r

    • V - voltage
    • K - constant
    • r - radius
  93. Voltage formula
    V = PE/q

    Voltage is equal to potential energy over charge
  94. Resistance formula
    R = pL/A

    • p - resistivity
    • L - length
    • A - cross-sectional area
  95. Capacitance formula
    U = 1/2 CV2

    U - PE

    C - capacitance

    V - voltage

    C = Q/V

    Q - charge
  96. Dielectric characteristics
    • Insulator
    • Polarizable
    • Resistor
    • Makes more charge build up on the plates
  97. Variables that affect capacitance
    • Plate area (directly related)
    • Plate thickness (no effect)
    • Distance between plates (inversely related)
    • Strength of dielectric (directly related)
  98. Capacitor charge vs. time graph
  99. Conceptual ideas of a battery
    • Positive terminal has highest electric potential.
    • Electrons build up on negative terminal and move to positive.
  100. Conceptual ideas of a resistor
    • There is always a voltage drop across any resistor.
    • Current through a resistor is inversely related to resistance. 2x resistance = 1/2 current.
  101. Solving circuits
    • Must be simplified, eg. no more than one of each component.
    • 1. Resistors in series: add directly
    • 2. Resistors in parallel: add the inverses and take the inverse
    • 3. Capacitors in series: add the inverses and take the inverse
    • 4. Capacitors in parallel: add directly
    • 5. Batteries in series: add directly
    • 6. Batteries in parallel: total voltage = the highest voltage of any one of the batteries in parallel
  102. Ohm's Law
    V = IR

    • V - voltage
    • I - current
    • R - resistance
  103. Electric power formula
    P = IV

    P - power
  104. AC vs. DC
    • Alternating current is created by a generator and can be represented by a sine wave.
    • Direct current is created by a battery.
  105. Fmagnet on a charged particle formula
    F = qvBsin

    • F - force

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