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ALTIUS > Physics 2 > Flashcards

Physics 2 Flashcards

1
Q
  • Think of a “FIELD” as:
A
  • an invisible influence capable of exerting a force on a MASS or CHARGE
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2
Q
  • Universal Law of Gravitation (formula)
A

Fg=Gm1m2/r2

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3
Q
  • The Universal Law of Gravitation is true everywhere, but NEAR EARTH’S SURFACE:
    1. What do we assume?
    2. What formula can we simplify to?
A
  • Assume g= 10 m/s2
    • Simplify to:
      • F=mg
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4
Q
  • Give the PEgrav formula NEAR EARTH

For FLUIDS (which DON’T always move as a single uni), what change to the formula do we make?

A

PEgrav=mgh

  • For fluids:
    • use PEgrav=pgh
      • p=density=m/v
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5
Q
  • Give the PEgravformula
    • IN SPACE, or
    • NEAR EARTH’S SURFACE
      • if we AREN’T assuming g=10 m/s2
A

PEgrav= - Gm1m2/r

Radius is NOT squared here!!!

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6
Q
  • Friction opposes ____, not ____
A

SLIDING!

  • ​not motion
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7
Q
  • If theres SLIDING, it’s ___ friction
  • If NOT, its ___ friction
A
  • sliding= kinetic friction
  • not sliding=static friction
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8
Q
  • Give the formulas for static & kinetic friction
A

STATIC FRICTION:

  • Ff=UsFn ​
    • or Ff=Usmgcosθ

KINETIC FRICTION:

  • Ff=UkFn
    • or Ff=Ukmgcosθ

​Us / Uk = Coefficient of static/kinetic friction

Fs / Fk= Force of static/kinetic friction

n= “normal force”=mgcosθ

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9
Q
  • Define MAX static friction
A
  • once this value is reached, OBJECT BEGINS TO SLIDE
    • at this moment, we now have kinetic friction, NOT STATIC

Ex: no mvmt at 500 N (static) but starts moving at 501 N=kinetic

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10
Q
  • Inclined Planes
    • Give the equation for:
      • Force down an inclined plane
        • parallel to the surface
A

F=mgsinθ

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11
Q
  • Inclined planes:
    • Normal force on an Inclined Plane
      • Equation=?
A

Fn=mgcosθ

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12
Q
  • Inclined planes:
    • Velocity of a particle at the base of an inclined plane
    • Equation=?
A

Vf=√2gh

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13
Q
  • Inclined planes
    • ACCELERATION down an inclined plane
    • Equation=?
A

a=gsinθ

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14
Q

Hooke’s Law formula

A

F=kΔx

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15
Q
  • How do you calculate k (spring constant) by hanging weights?
    • Remember calculation is different for just doing ONE trial and doing TWO (+) trials
A
  • Solve using Hooke’s Law
    • F=kΔx
    • for Δx, use:
      • _Displacement from equilibrium p_oint
        • for ONE trial
      • Difference in displacement
        • between TWO trials
    • For F, use:
      • Force applied in ONE trial, or
      • Difference in force
        • between TWO trials
  • Remember to convert mass of object to force
    • ​using F=mg
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16
Q
  • PEelastic
    • ​Definition
    • Equation=?
A

PEelastic=½kΔx2

  • PEelastic= PE stored in a compressed spring
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17
Q
  • PEelastic most likely used for what kinds of questions?
  • How would you use PEelastic to find out how far a spring compresses when an object hits it?
A

Conservation of energy questions!

  • When a mass of velocity V hits a spring:
    • ALL of its KE is converted into PEelastic
    • Setting KEinitial equal to final PEelastic
      • …lets you find how far the spring will compress
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18
Q
  • Kinetic Energy equation=?
A

KE=½mv2

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19
Q
  • Finding how far a spring compresses
    • What COMBINATION of formulas would you use?
A

Set KE equal to PEelastic

  • ​½mv2 = ½kΔx2
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20
Q
  • ONE CYCLE of a pendulum is?
    • (LOTR)
A
  • “There and back again”
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21
Q
  • For a pendulum to exhibit Simple Harmonic Motion (SHM)…
    • What value must be LOW?
A
  • Angle of displacement
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22
Q

Give 3 examples of Simple Harmonic Motion

A
  1. Pendulum
    • mass on a string
  2. Things w/ circular motion when viewed from the side
    • Ex: Something bobbing up & down in the water
      • has a circular motion!
  3. Waves sloshing back & forth in a container
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23
Q
  • Simple Harmonic Motion
    • Give the Mass on a Spring formula
A

T=2π√m/k

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24
Q
  • Simple Harmonic Motion
    • Give the pendulum formula
A

T=2π√L/g

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25
Q
  • Simple Harmonic Motion
    • What is “T?”
    • What thing is its inverse?
A

T=period

  • inverse to frequency
    • f=1/T
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26
Q
  • Objects at rest are in ___ equilibrium
A

STATIC equilibrium

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27
Q
  • Objects moving at CONSTANT velocity are in ___ equilibrium
A

DYNAMIC equilibrium

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28
Q
  • What do you do to solve equilibrium problems?
    • Hint: make a T…
A

Make a T

  • put opposing forces on opposite sides
  • balance them out
  • Ex: If 180 N in downward direction
    • then 180N upward
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29
Q
  • Give 3 examples of equilibrium
A
  1. Terminal velocity
    • mg=Fair
  2. Constant velocity
  3. Objects at rest
30
Q
  • Torque formulas3 variations)
    • Break down what each part represents
A
  1. T=fl
  2. T=mgl
  3. T=Frsinθ​
    • l=lever arm
    • r=dist b/t force & point of rotation
31
Q
  • In Torque equation:
    • r = l only when…?
    • What is always equal to “l?”
A

r = l only when θ=90°

  • “rsinθ” is always equal to l
32
Q
  • To solve for:
    • fulcrum and boards on strings problems
      • Hint: these are in equilibrium
A

Set:

  • Tclockwise=Tcounterclockwise
    • ​include ALL torques!
33
Q
  • Torque
    • In what scenario would you use T=Frsinθ?
A
  • When Force applied is NOT perpendicular to the surface
    • i.e., when θ is NOT 90°
34
Q
  • Define:
    • systems NOT in equilibrium
A
  • where the object has NON-ZERO ACCELERATION
35
Q
  • When solving for systems NOT in equilibrium:
    • How do you solve it differently than systems that are in equilibrium?
    • What can you IGNORE when solving for systems that are not in equilibrium?
A
  • Solve in same way as equilibrium problems (T method
    • but add “ma” to the “losing side”
      • This equals it out

You can IGNORE SIGNS (+/-) when you do this method!

36
Q
  • Equilibrium on an Inclined Plane
    • How to solve?
A

Use T method

  • One side= UP forces
  • Other side=DOWN forces
    • Down forces always equal to F=mgsinθ
      • since force of friction is always parallel to the plane opposite the direction of motion
37
Q

How to solve problems involving 2D forces

A

Use T method

  • Put formula that predicts component of each force into boxes
  • Add “ma” onto the “losing side”
38
Q

Define the “right hand rule” for angular velocity (ω)

A
  • Curl fingers around axis of rotation, so that fingers are pointing in the direction of rotation
    • Your thumb will then be pointing in the direction of the vector (ω)
39
Q

How many radians per 1 revolution

A

~6

  • 6.28 exactly
40
Q

How to convert Radians to degrees

A
  • 2π radians/360°

or

  • π radians/180°
41
Q
  • An object is in rotational equilibrium IF:
    • 2 options…either one or the other
A
  1. It is NOT rotating, or
  2. It is rotating with constant ω (angular velocity)
42
Q
  • Momentum formula=?
A

p=mv

43
Q
  • Think of momentum as?
    • When is it always conserved?
A

…as INERTIA INCREASED BY VELOCITY

  • p is always conserved in an isolated system
    • is not conserved when not in an isolated system
44
Q
  • Define “Impulse”
A
  • change in an object’s momentum
    • “Δp”
45
Q
  • Impulse formula
    • 3 variations (in order of how you should think of impulse)
A
  1. I=Δp
  2. I=mΔv
  3. I=Favgt
46
Q
  • What are common impulse questions?
    • How are velocity and impulse related?
A

CAR CRASHES!

  • No change in V= No impulse
  • High change in V=High impulse
47
Q
  • Elastic vs Inelastic collisions
A

Elastic Collisions

  • p AND KE conserved

Inelastic Collisions

  • p conserved ONLY
48
Q
  • If object is deformed during collision, it was a _____ collision
A
  • inelastic
49
Q
  • Elastic collisions
    • Equation=?
    • Hint: What gets conserved during elastic collisions?
A

½m1v12+ ½m2v22= ½m1v12+ ½m2v22

  • p and KE both conserved
50
Q
  • For PERFECTLY elastic collisions, what 2 weird things happen?
    • What’s a (albeit imperfect, but close enough) example of this?
A
  1. Speed is conserved
    • before AND after collision
  2. If mass of 2 objects is equal but they have different velocities:
    • velocities get exchanged
      • in order to conserve momentum (p=mv)

Think of: BILLIARD BALLS

51
Q
  • Inelastic collisions formula
    • What thing DO you need to remember to use here that you DON’T need to use for elastic collisions?
A

m1v1+m2v2=m1v1+m2v2

You need to remember to USE SIGNS!! (+/-)

  • Velocity has a negative sign when:
    • going to the LEFT or
    • DOWN
52
Q
  • “Perfectly INelastic” collisions
    • definition & formula
A
  • objects collide and stick together
    • it’s like MARRIAGE!
  • if they move after collision, they do so together

m1v1+m2v2=(m1+m2)v3

53
Q
  • Reverse Collisions definition
    • What is commonly use by the MCAT to test you on reverse collisions?
A
  • Two objects start out together and come apart
    • it’s like DIVORCE

Common examples:

  • Bomb exploding
  • Also, RADIOACTIVE DECAY is frequently used
54
Q
  • Thermal expansion formula
A

ΔL=αLoΔT

55
Q
  • Heating solids leads to ___
  • Cooling solids leads to ___
A
  • expansion
  • shrinkage
56
Q
  • What makes water unique when it comes to thermal expansion?
A
  • When temperature of water gets close to zero, it EXPANDS (INSTEAD OF SHRINKING)
    • because of of highly ordered lattice structure of ice
      • This is why the solid ice doesnt sink on liquid water
57
Q
  • PEelec
    • formula=?
    • 2 variations
A
  • PEelec=Kq1q2/r

or

  • PEelec=qEd
58
Q
  • PEcapacitor formula=?
    • 3 variations
A
  • PEcapac=½QV
  • PEcapacitor=½CV2
  • PEcapacitor=½Q2/C
59
Q
  • Internal energy
    • definition
A
  • Energy of:
    • Internal vibrations &
    • Random motions of:
      • molecules and/or
      • atoms w/

…in a system

60
Q
  • Heat energy
    • Definition
    • Where can Heat Energy come from? (2)
A

=energy dissapated as heat

  • Can come from:
    1. a collision
    2. a current-carrying wire

(among other things)

61
Q
  • Law of Conservation of Energy says…?
A
  • in an isolated system:
    • energy is *ALWAYS* *CONSERVED*
      • e.g., it can be transferred, but never lost
62
Q
  • Define an “Open system”
A
  • both mass AND energy
    • ​…can be exchanged with surroundings
63
Q

Define a “Closed system”

A
  • Energy, but NOT mass
    • …can be exchanged with the surroundings
64
Q
  • Define an “Isolated system”
A
  • Neither mass NOR energy
    • ​…can be exchanged with the surroundings
65
Q
  • Think of “Work” in what order?
    • …when it comes to formulas
A
  1. W=ΔE
  2. W=Fdcosθ
66
Q
  • When I see the following, Ill think “WORK”
    • 7 things
A
  1. Change in velocity
  2. Change in height
  3. Change in positon of masses (or planets in space)
  4. Change in position of a charge
  5. Compression of a spring (PE stored up)
  6. Friction
  7. Air resistance
67
Q
  • Give 2 examples of W=Fdcosθ​
    • aka…give 2 examples of force being applied along a displacement
A
  1. Pushing a block along a table
  2. An object falling from height
    • height=displacement!
      • Dont forget that!
68
Q
  • What are the ONLY 2 ways energy can be transferred in/out of a system?
A
  1. Work
  2. Heat (dissapated)
69
Q
  • 1st Law of Thermodynamics
    • Equation=?
A

ΔE= W + Q

70
Q
  • Work-Energy theorem
    • What should you focus on instead?
A
  • If Fnet does work on a rigid object:
    • the work done on that object is equal to:
      • the change in KE of the object
  • Focus on W=ΔE
    • correct use of this negates need to use work-energy theorem
71
Q
A

ALTIUS (27 decks)

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