Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Physics > Topic 2 Mechanics > Flashcards

Topic 2 Mechanics Flashcards

You may prefer our related Brainscape-certified flashcards:
Physics 101 flashcards AP® Physics flashcards
1
Q

scalars

A

no direction only size
- mass
- energy
- temperature
- distance
- power
- speed
- time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

vectors

A

both direction and size
- pressure
- force
- acceleration
- magnetic/electric/gravitational field strength
- displacement
- momentum
- velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

distance definition

A

how far you have travelled (m)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

displacement definition

A

the distance revelled in a particular direction (m)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

speed definiiton

A

the rate of change of distance (distance/t)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

velocity definition

A

the rate of change of displacement (displacement/t)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

instantaneous speed definition

A

the rate of change of distance at one particular time (ms^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

average speed definition

A

the speed over a period of time (ms^-1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

acceleration definition

A

rate of change of velocity (v/t) ms^-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

when should you use equations of motion eg. v=u+at

A

if an object is accelerating at a constant rate ie. undergoing uniform acceleration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

gradient of displacement-time graph represents

A

velocity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

gradient of velocity-time graph represents

A

acceleration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

area below line of velocity-time graph represents

A

displacement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

area below line of acceleration-time graph represents

A

change in velocity (*still speeding up but the increase of velocity is getting less)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

area below line of acceleration-time graph represents

A

change in velocity (*still speeding up but the increase of velocity is getting less)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

area above x-axis of displacement graph represents

A

displacement in a positive direction, eg to the right of the origin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

area below x-axis of displacement graph represents

A

displacement in a negative direction, eg. to the left of the origin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

area above x-axis of velocity graph represents

A

motion in a positive direction (regardless of position)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

area below x-axis of velocity graph represents

A

motion in a negative direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

area above x-axis of acceleration graph represents

A

acceleration in a positive direction (shows the direction of the net force)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

area below x-axis of velocity graph represents

A

acceleration in a negative direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

relative velocity definition

A

the apparent or relative velocity of an object depends on the situation of the observer (called their frame of reference)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

projectile motion definition

A

a projectile is an object moving through the air under the influence of only one force - gravity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

why does the trajectory (path) of a projectile motion follows a parabola?

A
  • VERTICAL component of velocity is constantly CHANGING (due to the force of gravity)
  • HORIZONTAL component of the velocity is CONSTANT (assuming no air resistance)
  • at the top vertical velocity = 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

how does the trajectory of a projectile motion object change with air resistance?

A
  • shorter range
  • lower maximum height that is reacher earlier
  • gradient steeper on way down
    see pg 16 topic 2 book for picture
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

projectile problems: horizontally, eg fired of cliff
what is the initial vertical velocity and horizontal velocity

A

initial vertical velocity = 0
horizontal velocity = launch velocity, v

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

projectile problems: at an angle above the horizontal
what is the initial vertical velocity and horizontal velocity

A

initial vertical velocity = v sinθ
horizontal velocity = v cosθ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

projectile problems: at an angle below the horizontal
what is the initial vertical velocity and horizontal velocity

A

initial vertical velocity = v sinθ
horizontal velocity = v cosθ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

projectile motion:
vertical motion is considered when calculating ________________
horizontal motion is considered when calculating ________________

A

VERTICAL motion is considered when calculating maximum HEIGHT reached or TIME of flight
HORIZONTAL motion is considered when calculating RANGE

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

points to remember for projectile problems

A
  • at the highest point vertical velocity is zero
  • acceleration is always downwards at 9.81ms^–2
  • horizontal velocity is constant
  • range = horizontal velocity x time of flight
  • problems may be solved using kinematic equations of conservation of energy
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what equation is used for VERTICAL motion
(max height, time in air)

A

s = ut + 1/2 at^2
v^2 = u^2 + 2as
v = u + at

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what does fluid resistance (drag) depend on

A
  • the velocity of the object relative to the fluid
  • the size and shape of the object
  • the fluid used (its viscosity)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

fluid resistance definition

A

when an object moves through a fluid (liquid or a gas), there will be a frictional fluid resistance (drag) acting against the object’s motion

34
Q

free-fall definition

A

when an object falls through under the influence of gravity it will initially accelerate at 9.81ms^–2. in certain situations (eg. very dense objects falling), air resistance can be ignored and the object is said to be in free-fall.

35
Q

terminal velocity definition

A
  • In reality, air resistance will affect the motion of falling objects. The magnitude of the air resistance will increase as the object’s velocity increases.
  • The object will continue to accelerate but at less than 9.81ms-2.
  • Once the magnitude of the upwards air resistance is equal to the downwards gravitational force (weight), the object will no longer accelerate as the forces on the object are now balanced.
  • Its speed will remain constant and is called terminal velocity.
36
Q

On graph what will terminal velocity look like?

A

straight line near the end, see pg 19 topic 2 book

37
Q

mass (m) definition

A

the amount of matter in an object (kg). it does not change with a change in position

38
Q

weight (W) definition

A

the force of gravity actin got an object (N). it will change if an object changes its position

39
Q

gravity causes every…..

A

object in the universe to attract every other object with a force because of gravity.

40
Q

size of gravity depends on

A
  • the mass of the objects (more mass, more force)
  • the distance between the objects (more distance, less force)

on Earth the strength of gravity is 9.81 Nkg^–1

41
Q

weight =

A

mass x gravity (W=mg)

42
Q

force defintion

A

basically a push or a pull (N)

43
Q

free body diagram definition

A

a drawing that shows all the forces acting on an object

44
Q

free body diagram weight direction

A

always straight down

45
Q

free body diagram normal reaction

A

When an object pushes down on a surface, the surface pushes back on the object. The normal reaction force is always at 90º to the surface the object is on

46
Q

free body diagram thrust

A

A push force, e.g. from an engine

47
Q

free body diagram friction

A

A force that is always in the opposite direction to any motion. If it is due to air then it is called air resistance

48
Q

free body diagram buoyancy

A

A support force from a fluid e.g. water or air

49
Q

free body diagram lift

A

The upwards push on the wings of an aircraft due to its motion through air

50
Q

free body diagram tension

A

The pull force due to a rope or chain

51
Q

is the velocity changing when forces are balanced

A

not changing

52
Q

is the velocity changing when forces are balanced

A

not changing
if upwards forces = downwards forces, and left forces = right forces, then forces are balanced. object will remain at rest of continue to move in straight line at constant speed, net force = 0 and there is no acceleration

53
Q

is the velocity changing when forces are unbalanced

A

changing
forces are greater in one direction than the other, forces are unbalanced and object will accelerate in the direction of the greater force. The acceleration is produced by the overall (or net) force on the object

54
Q

Newton’s first law

A

“an object continues in uniform motion in a straight line or at rest unless a resultant external force acts”

which basically means that a resultant force causes acceleration, and no resultant force
means no acceleration. The acceleration is in the direction of the resultant force.

If the resultant force on an object is zero, it will not be accelerating and is then said to be
in translational equilibrium (moving in a straight line at a constant speed).

55
Q

Newton’s second law

A

“the resultant force on an object is proportional to the acceleration providing the mass of the object remains constant”
F = ma

56
Q

Newton’s third law

A

“for every action on one object there is an equal but opposite reaction on another object”

eg. I am attracted towards the Earth by gravity: the earth is attracted towards me by gravity

eg. two cars collide and both exert the same size force on each other

57
Q

normal reaction force’s impact on how heavy we feel eg. lift

A
  • stationary or moving at constant velocity, r=w=mg, feel usual weight
  • accelerating upwards, r–w = ma r = w+ma = m(g+a), feel heavier
  • accelerating downwards, w–r=ma r= w–ma = mg–ma r = m(g–a), feel lighter
  • cable cut and falling, w–r = mg r = w–mg = mg–mg r=0, feel weightless
58
Q

resolving forces definition

A

break down a force into two components see pg 29 topic 2 book for example

59
Q

resultant forces

A

the sum of all the forces acting on an object
F = √F1^2 + F2^2
θ = arctan(F1/F2)

60
Q

resultant forces in equilibrium

A

all forces acting on it will add up to zero so Fnet = 0

If Fnet = 0, then a closed triangle can be drawn

pg 30 topic 2 book

61
Q

object on incline, weight force’s two forces

A
  • parallel to the slope (mg sinθ)
    (= friction if speed constant)
  • perpendicular to the slope (mg cosθ)
    (= normal reaction)
62
Q

static friction definition

A

when a force is applied to an object resting on a surface, but the force is not large enough to move the object

occurs when there is no relative motion between the surfaces
(cannot be negative value)

63
Q

dynamic friction definition

A

once the object exceeds the maximum value of static friction force Ff the object will begin to slide.

occurs when there is relative motion between the surfaces

64
Q

coefficients of friction: bigger number, _____________ force required ie. ____________ _________ friction

A

bigger number, bigger force required ie. more static friction

65
Q

measuring coefficient of static friction on slope:
Ff (friction force) =
R =

A

Ff = mg sinθ

R = mg cosθ

66
Q

energy definition

A

“the capacity to do work”

means you need energy for things to happen or for work to occur

67
Q

Hooke’s law

A

the extension of a spring is proportional to the applied force

F = KΔX
K = spring constant (Nm^–1)
ΔX = extension or compression (m)

68
Q

conservation of energy

A

energy can be converted from one type to another. it cannot be created or destroyed.

69
Q

work (J) definition

A

work is said to be done when a force (F) moves an object through a displacement (s). Work is therefore a transfer of energy

70
Q

formulas for work

A

work done (J) = force (N) x displacement (m)
W(J) = F(N) s(m) cosθ

71
Q

how to work out work done from graph

A

if the force being used is not constant then the work done can be calculated by either using the average force value or by calculating the area below a force-displacement graph

72
Q

how to work out work done where an object is being lifted

A

the force required to life the object is equal to the object’s weight

73
Q

power definition

A

the rate which work is done or energy is transferred (W or Js^–1)

74
Q

efficiency definiton

A

a ratio of how much work, energy or power we get out of a system compared to how much is put in

75
Q

linear momentum definiton

A

the product of mass and velocity

76
Q

what is the conservation of momentum

A

“the total linear momentum of a system remains constant provided no resultant external force acts (eg. friction)”

77
Q

elastic collision

A

no kinetic energy is lose during the collision. in reality it only occurs between sub-atomic particles

78
Q

inelastic collision

A

kinetic energy is lost

79
Q

impulse definition

A

the change in momentum (Δp or FΔt)
units: kgms^–1 or Ns

impulse = FΔt = Δp
*if F is changing, use the average force

80
Q

how to find impulse on a _____-_____ graph

A

on a force-time graph, impulse is the area below the graph

81
Q

explain explosions

A
  • an explosion can be treated as a collision. typically a stationary system will break apart into two pieces.
  • as with collisions, total momentum is conserved and will be equal to zero
  • kinetic energy will always increase in an explosion (as it was 0 before)
  • the kinetic energy comes from the energy source of the explosion
  • see pg 48 topic 2 booklet for example
82
Q

example of explosions

A
  • recoil of gun
  • ice skaters
  • “zero-g” situations

Physics (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions