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y1 statistics and mechanics > Ch.8 Modelling in mechanics > Flashcards

Ch.8 Modelling in mechanics Flashcards

1
Q

what axis does the unit vector i travel along?

A

x

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2
Q

what axis does the unit vector j travel along?

A

y

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3
Q

what are the 3 base SI units commonly used in mechanics?

A
  1. Mass, kilogram, kg
  2. Length/displacement, metre, m
  3. Time, second, s
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4
Q

what is a vector quantity?

(mech)

A

a quantity with both magnitude and direction

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5
Q

what is a scalar quantity?

A

a quantity with no direction, only magnitude

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6
Q

what are some examples of scalar quantities?

A

distance and speed

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7
Q

what is a particle model?

A

an object with negligible dimensions

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8
Q

what are the modelling assumptions made when an object is modelled as a particle?

A
  • the mass of the object is concentrated at a single point
  • rotational forces and air resistance can be ignored
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9
Q

what is the rod model?

A

all dimensions but one are negligible, like a pole or beam

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10
Q

what are the modelling assumptions made when something is modelled as a rod?

A
  • mass is concentrated along a line
  • it has no thickness
  • it is rigid ( does not bend or buckle )
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11
Q

what is a lamina model?

A

an object with area but negligible thickness, like a sheet of paper

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12
Q

what are the modelling assumptions made when something is modelled as a lamina?

A
  • it’s mass is distributed across a flat surface
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13
Q

what does uniform body mean in math modelling?

A

the mass is distributed evenly

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14
Q

what are the modelling assumptions made when something is modelled with a uniform body?

A

the mass of the object is concentrated at a single point ar the geometrical centre of the body - the centre of mass

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15
Q

what is a light object model?

A

when the mass of the object is small compared to other masses, like a string or pulley

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16
Q

what are the assumptions made with a light object model?

A
  • treat object as having zero mass
  • tension is the same at both ends of a light string
17
Q

what is an inextensible string model?

A

a string that does not stretch under load

18
Q

what is the assumption made with an inextensible string model?

A

acceleration is the same in objects connected by a taut inextensible string

19
Q

what is the assumption made with a smooth surface in mechanical modelling?

A

assume that there is no friction between the surface and any object on it

20
Q

what is the assumption with a rough surface in mechanical modelling?

A

objects in contact with the surface experience a frictional force when moving

21
Q

what is a wire model?

A

a rigid thin length of metal

22
Q

what is the modelling assumptions with a wire model?

A

it is treated as one dimensional

23
Q

what are the modelling assumptions with a smooth and light pulley?

A
  • the pulley has no mass
  • tension is the same on either side of the pulley
24
Q

what is the bead model?

A

a particle with a hole in it for threading on a wire or string

25
Q

what are the modelling assumptions for a bead model?

A
  • moves freely along a wire or string
  • tension on either side of the bead is the same
26
Q

what is the peg model?

A

a support from which a body can be suspended or rested

27
Q

what are the modelling assumptions for a peg model?

A
  • it is dimensionless and fixed
  • can be rough or smooth as specified in question
28
Q

what is air resistance in mechanical modelling?

A

resistance experienced as an object moves through the air

29
Q

what is the modelling assumptions for air resistance?

A

usually negligible

30
Q

what is gravity in mechanical modelling?

A

a force of attraction between all objects and the ground
- acceleration due to gravity is demoted by g

31
Q

what are the modelling assumptions with gravity?

A
  • assume all objects with mass are attracted towards earth
  • earth’s gravity is uniform and acts vertically downwards
  • g is a constant which is 9.8 unless otherwise stated in the question

y1 statistics and mechanics (11 decks)

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