Modelling assumptions Flashcards
particle
dimensions of object are negligible
mass of object conc. at single point
rotational forces + air resistance ignored
rod
all dimensions but one negligible (like pole)
mass con. along line
no thickness
rigid (can’t bend/buckle)
lamina
area but negligible thickness (paper)
mass distributed across a flat surface
uniform body
mass is distributed evenly
mass of object conc. at single point at geometrical centre of body (centre of mass)
light object
small mass (like string/pulley)
treated with zero mass
same tension at both ends of light string
inextensible string
string that doesn’t stretch under load
acceleration same in objects connected by taut inextensible string
smooth surface
assume no friction between surface and objects in contact
rough surface
not smooth (lol) objects while moving in contact will experience frictional force
wire
rigid thin length of metal
treated as 1D
smooth and light pulley
all pulley considered smooth and light
no mass
tension same on either side of pulley
bead
particle with hole in it for threading with wire/string
moves freely along wire/string
tension same on either side of bead
peg
a support from which a body can be suspended or rested
dimensionless
fixed
can be rough or smooth (specified)
air resistance
resistance experienced as inject moves through air
negligibility specified in question
gravity
force of attraction between all objects
acceleration due to gravity denied by g
assume all objects with mass attracted towards Earth
Earth’s gravity uniform and acts vertically downwards
g = 9.8m s^-2 unless stated otherwise