dynamics Flashcards
1
Q
dynamics
A
the study of why things move
2
Q
force
A
push or pull on an object
3
Q
four fundamental forces
A
- gravity
- electromagnetic
- weak nuclear
- strong nuclear
4
Q
gravitational force
A
- Fg
- towards ground on all objects
5
Q
force of friction
A
- Ff
- prevents slip/slide
- opposite of motion
6
Q
applied force
A
- FA
- in direction that object is being pushed
7
Q
normal force
A
- FN
- perpendicular to surface
8
Q
tension
A
- FT
- in direction of pulling
9
Q
air resistance
A
- Fair
- opposite of motion going though air
10
Q
newton’s first law
A
- law of inertia
- object will maintain state of rest until acted upon by outside force
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)
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
13
Q
two important relationships about newton’s second law
A
- mass inversely proportionate to acceleration
- net force directly proportionate to acceleration
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
15
Q
gravitational force
A
- FG
- attracts objects w/ mass together
- action at distance force
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
kinetic friction
force that opposes motion once object is in motion
26
is static or kinetic friction greater? why?
- static friction
- law of inertia states tht. its harder to get objects to acc. start moving
27
seatbelts
- 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
airbags
- 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
headrest
- 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
crumple zone
- 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
define gravity
- attractive force between all matter
- weakest force
- infinite range
32
define electromagnetic force
- caused by electrical charges, holds atoms/molecules together
- attractive and repulsive
- infinite range
33
define weak nuclear
- responsible for radioactive decay (one element transformed into another)
- short range
34
define strong nuclear
- holds protons and neutrons together in nucleus
- short range
