8. modelling in mechanics

Question 1

rod model

Answer 1

all dimensions but one are negligible (like pole)

Question 2

rod assumptions

Answer 2

mass concentrated along a line
no thickness
rigid

Question 3

inextensible string model

Answer 3

string that does not stretch under load

Question 4

inextensible string assumption

Answer 4

acceleration is the same in objects connected by an inextensible string

Question 5

model particle

Answer 5

dimension of object are negligible

Question 6

assumptions of particle

Answer 6

mass of object is concentrated at a single point
rotational forces/ air resistance can be ignore

Question 7

gravity model

Answer 7

forces of attraction between all objects
acceleration due to gravity denoted by g 9.8

Question 8

assumptions of gravity

Answer 8

assumes all objects with mass attracted towards earth
constant 9.8m/s^2
earth gravity is uniform acts vertically downwards

Question 9

air resistance model

Answer 9

resistance experiences as object moves through air

Question 10

air resistance assumptions

Answer 10

modelled as being negligible

Question 11

peg model

Answer 11

a support from which a body can be suspended/rested

Question 12

ped assumptions

Answer 12

dimensionless
can be rough or smooth as specified

Question 13

lamina model

Answer 13

object with area but negligible thickness like paper

Question 14

lamina assumptions

Answer 14

mass distributed across a flat surface

Question 15

wire model

Answer 15

rigid thin length of metal

Question 16

wire assumptions

Answer 16

treated as one dimensional

Question 17

light object model

Answer 17

mass of object is small compared to other masses

Question 18

light object assumptions

Answer 18

treat object as having zero mass
tension the same at both ends of string

Question 19

uniform body model

Answer 19

mass distributed evenly

Question 20

uniform body assumptions

Answer 20

mass of object concentrated at a single point at centre of the body
centre of mass

Question 21

rough surface model

Answer 21

surface is not smooth but rough

Question 22

rough surface assumptions

Answer 22

object in contact with surface experiences a frictional force if there moving acted on by a force

Question 23

smooth surface assumptions

Answer 23

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

Question 24

smooth light pulley model

Answer 24

all pulleys would be considered smooth and light

Question 25

smooth pulley assumptions

Answer 25

has no mass tension is the same on either side of the pulley

Question 26

bead model

Answer 26

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

Question 27

bead assumptions

Answer 27

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