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Ortho BMSc > Mechanics: Unit 1 Motion (class + online) > Flashcards

Mechanics: Unit 1 Motion (class + online) Flashcards

1
Q

What is mechanics?

A

a branch of physics that analyses the action of forces on matter or material bodies

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2
Q

What is force?

A

something that displaces and/or deforms a body

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3
Q

What can statics be used for?

A

to calculate unknown forces

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4
Q

Which of kinetics and kinematics considers force?

A

kinetics

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5
Q

What is kinematics?

A

it quantifies motion by how it moves in 3d space

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6
Q

What is kinetics?

A

looks at the relationship between force and motion

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7
Q

What are the two areas of mechanics?

A

rigid and deformable body

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8
Q

In classical mechanics, what do the terms
a) reductionistic
b) deterministic
mean?

A

a) reducing a complex problem into simpler parts

b) if we have a set of initial conditions we can work forward/bckward and distinguish a solution

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9
Q

What is a translational movement?

A

a linear movement ie. in a straight line

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10
Q

What is the difference between rectilinear and curvilinear?

A

rectilinear is an actual straight line whereas curvilinear isnt perfectly straight but there is no rotation

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11
Q

What do rotary movements in walking allow for?

A

linear movement of the whole body

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12
Q

What system is used for measurement?

A

SI aka metric

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13
Q

How do we measure

a) length
b) time
c) mass

A

a) metre
b) second
c) kilogram

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14
Q

how many metres in

a) km
b) cm
c) mm
d) micrometre

A

a) 1000
b) 0.01
c) 0.001
d) 0.000001

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15
Q

what is angular distance and which SI unit does it use?

A

the total angle turned through

rads

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16
Q

what is a rad ? and what is it equal to?

A

2 π rads = 360

about 57 degrees

one radian encloses an arc which has a length equal to the circle radius

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17
Q

what is a newton?

A

kilogram metres per second squared

kg m s-2

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18
Q

what are the four basic physical quantities?

A

time
angle
temperature
distance

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19
Q

What symbol represents

a) angle in degrees?
b) angle in rads?

A

a) phi Φ

b) theta θ

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20
Q

How do we convert radians to degrees ?

A

degrees = (radians x180/ π)

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21
Q

How do we convert degrees to radians?

A

radians = (degrees xπ /180)

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22
Q

What does zero degrees kelvin represent?

A

the point at which matter has no energy

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23
Q

How can you convert celsius to kelvin?

A

add 273

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24
Q

What are positions and directions given in reference to?

A

a reference frame

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25
Q

What are the two co-ordinate systems that positions in reference frames are related to?

A

the rectangular co-ordinate system or the polar co-ordinate system.

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26
Q

What is another name for the rectangular reference frame?

A

cartesian

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27
Q

What is a vector?

A

a quantity with magnitude (length) and direction

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28
Q

What is a scalar?

A

a quantity with only magnitude

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29
Q

Name some vectors

A 
displacement (inc angular)
velocity (inc angular)
force
momentum
acceleration
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30
Q

Name some scalars

A 
distance
speed
angle
rotation rate
mass
temperature
energy
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31
Q

What is the difference between distance and displacement?

A

distance is a scalar because it is just a measure of how far but displacement is a vector because it also takes direction into account

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32
Q

What is angular displacement?

A

when something is rotated through an angle in a clockwise or anticlockwise direction

has both a magnitude and a direction

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33
Q

How do you add or subtract two or more vectors?

A

via graphs or trigonometry to give a resultant vector

34
Q

When resolving a vector, if the resultant vector faces

a) north west (ie. positive vertical but negative horizontal)
b) south west (ie. negative vertical and horizontal)

how do we calculate the angle?

A

a) +180

b) -180

35
Q

What do you call axes which are all at right angles to each other?

A

orthogonal

36
Q

in which type of system does a change in one axis not affect the others?

A

orthogonal

37
Q

describe a plane

A

a 2d structure with no thickness encompassing 2 axes of a 3D co-ordinate system

38
Q

what happens when 2 planes cross each other?

A

a straight line is formed

39
Q

how many planes can be at right angles to each other?

A

max is 3

40
Q

how is position expressed in the polar coordinates system for 2D structures?

A

(rc, θc)

where rc = length of line
θc = angle of line

41
Q

When are polar co-ordinates more useful than rectangular co-ordinates?

A

in the studies of circular objects and where angles and rotations are important

42
Q

What is the origin?

A

the point where all axes cross (0,0,0)

43
Q

What is the difference between speed and velocity?

A

speed is a scalar, the rate of change of distance travelled

velocity is a vector, the rate of change of displacement (so direction is included)

44
Q

What are the SI units of velocity?

A

metres per second (m s-1)

45
Q

how do you work out the average velocity?

A

change in displacement over time

46
Q

What is acceleration?

A

the rate of change of velocity

47
Q

Is acceleration a scalar or a vector quantity?

A

a vector quantity

48
Q

What are the SI units of acceleration?

A

m s-2

49
Q

What is the SI unit of force?

A

the newton (N)

50
Q

how is position expressed in the polar coordinates system for 3D structures?

A

(rc, θc, Φc )

51
Q

What do we call the movement of an object in a straight line with no rotation taking place?

A

translation

52
Q

What do we call the movement of an object in a circular path with no translation taking place?

A

a rotation

53
Q

How many degrees of freedom does unconstrained movement have?

A

6 degrees of freedom

  • 3 translational (x,y,z)
  • 3 rotational
54
Q

how many degrees of freedom does a snooker ball have rolling on a table?

A

5 degrees of freedom

  • 2 translational
  • 3 rotational
55
Q

how many degrees of freedom does a door handle have?

A

1 rotational

56
Q

compare the degrees of freedom of a ball and socket joint to a hinge joint?

A

ball and socket eg hip has 3 rotational

hinge joint eg knee has 1 rotational

57
Q

How do we display velocity data?

A

displacement-time graphs

with velocity being equal to the gradient

58
Q

What is instantaneous velocity and how do we work it out?

A

it is the velocity at an instant in time
it is equal to the gradient on the displacement-time graph at a certain point
work it out by drawing a tangent

59
Q

How do we work out average acceleration?

A

change in velocity over time

= ms-2

60
Q

What is the acceleration of something falling due to gravity?

A

9.81m/s2

61
Q

How do we display acceleration data?

A

velocity-time graph

62
Q

What is the gradient of the velocity-time graph equal to?

A

acceleration

63
Q

What is the area under the velocity-time curve equal to?

A

total displacement ie the velocity

64
Q

What are the four parameters used to describe rotary motion?

A

time
angular displacement
angular velocity
angular acceleration

65
Q

What does the symbol a represent?

A

alpha is used to represent angular acceleration (rad/s2)

66
Q

what does the symbol ω represent?

A

omega is used to represent angular velocity (rad/s)

67
Q

what is angular velocity?

A

the angular displacement travelled per second

68
Q

how can we find the angular velocity?

A

plotting an angle-time graph

69
Q

what is angular acceleration?

A

the rate of change of angular velocity

70
Q

what is the gradient of an angular velocity-time graph equal to?

A

angular acceleration

71
Q 
what do
a) u
b) v
c) a
d) s
e) t
represent in the equations of linear motion?
A

a) starting velocity
b) final velocity
c) acceleration
d) displacement
e) time taken

72
Q

How can we calculate final velocity?

A

v = u + at

final velocity = starting velocity + (acceleration x time)

73
Q

Give 3 linear equations including displacement

A

v2 = u2 + 2as

s = 1/2 ( u + v) t

s= ut + 1/2 a t2

74
Q

What is the multiplication factor for the prefix giga?

A

10 to the 9

75
Q

What is the multiplication factor for the prefix mega ?

A

10 the 6

76
Q

What is the multiplication factor for the prefix kilo?

A

10 to the 3

77
Q

What is the multiplication factor for the prefix centi?

A

10 to the -2

78
Q

What is the multiplication factor for the prefix milli?

A

10 to the -3

79
Q

What is the multiplication factor for the prefix micro?

A

10 to the -6

80
Q

What is the multiplication factor for the prefix nano?

A

10 to the -9

81
Q

What is the symbol for angular displacement?

A

θ

82
Q

How can we measure force?

A

calibrated spring balance

Ortho BMSc (14 decks)

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