dynamics Flashcards

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1
Q

dynamics

A

the study of why things move

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2
Q

force

A

push or pull on an object

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3
Q

four fundamental forces

A
  • gravity
  • electromagnetic
  • weak nuclear
  • strong nuclear
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4
Q

gravitational force

A
  • Fg
  • towards ground on all objects
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5
Q

force of friction

A
  • Ff
  • prevents slip/slide
  • opposite of motion
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6
Q

applied force

A
  • FA
  • in direction that object is being pushed
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7
Q

normal force

A
  • FN
  • perpendicular to surface
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8
Q

tension

A
  • FT
  • in direction of pulling
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9
Q

air resistance

A
  • Fair
  • opposite of motion going though air
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10
Q

newton’s first law

A
  • law of inertia
  • object will maintain state of rest until acted upon by outside force
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11
Q

inertia

A
  • property of matter that states objects resist changes in their state of motion (inc. rest)
  • inertia is directly proportional to mass (heavier=harder to start/stop)
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12
Q

newton’s second law

A
  • if there is a net force acting on an object, the object will accelerate in the direction of that net force
  • mathematical rep. as: F=ma
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13
Q

two important relationships about newton’s second law

A
  • mass inversely proportionate to acceleration
  • net force directly proportionate to acceleration
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14
Q

newton’s third law

A
  • every action has an equal and opposite reaction
  • if object A exerts a force on object B, then object B exerts an equal and opposite force on object A
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15
Q

gravitational force

A
  • FG
  • attracts objects w/ mass together
  • action at distance force
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16
Q

action at distance force

A

forces that don’t touch us

17
Q

gravitational force depends on…

A
  • increased mass = increased force
  • increased distance = less force (F=1/r^2) bc. impact is so vast
18
Q

newton’s law of universal gravitation

A
  • tells us the gravitational attraction between objects
  • it’s that long equation
19
Q

what is weight

A
  • Fg
  • gravitational force acting on an object
20
Q

what are gravitational field strength and gravitational acceleration

A
  • grav. field strength: strength of a planet itself, N/kg
  • acceleration: acceleration experienced by objects due to grav. field
21
Q

what happens during freefall?

A
  • apparent weight = 0, feel weightless
  • upwards: Fn greater than Fg
  • downwards: Fg greater than Fn
22
Q

friction

A

force preventing motion in the direction opposite of motion

23
Q

surface friction caused by…

A

microscopic irregularities in surface that catch as they move past each other

24
Q

static friction

A
  • force that opposes attempted motion between stationary objects
25
Q

kinetic friction

A

force that opposes motion once object is in motion

26
Q

is static or kinetic friction greater? why?

A
  • static friction
  • law of inertia states tht. its harder to get objects to acc. start moving
27
Q

seatbelts

A
  • when car brakes, body will keep moving (inertia)
  • seatbelt prevents body from moving forwards into window
  • person exerts force onto seatbelt instead and seatbelt returns that force (3rd law)
28
Q

airbags

A
  • increase the time it takes to decelerate, thus decreasing force and impact
  • seatbelt acc. loosens to let person onto airbag bc. airbag beter at decreasing impact
  • a=v2-v1/t
29
Q

headrest

A
  • when hit from behind, body wants to move but seat prevents it, however head would snap back
  • first law: body moves, head stays
  • headrest should be close to head bc. third law: head hits headrest, headrest exerts force to head
30
Q

crumple zone

A
  • front of car absorbs energy and lengthen duration of impact
  • lengthened duration = less force on passengers
  • f=ma (2nd law) bc. more time=less acceleration=less force
31
Q

define gravity

A
  • attractive force between all matter
  • weakest force
  • infinite range
32
Q

define electromagnetic force

A
  • caused by electrical charges, holds atoms/molecules together
  • attractive and repulsive
  • infinite range
33
Q

define weak nuclear

A
  • responsible for radioactive decay (one element transformed into another)
  • short range
34
Q

define strong nuclear

A
  • holds protons and neutrons together in nucleus
  • short range