Modelling in Mechanics Flashcards
what is the particle model
when the dimensions of the object are negligible
what is the rod model
all dimensions but one are negligible
what are the modelling assumptions of the particle model
- mass of object concentrated at a single point
-rotational forces and air resistance can be ignored
what are the modelling assumptions of the rod model
-mass concentrated along a line
-no thickness
-rigid (does not bend or buckle)
what does the lamina model mean
an object with area but negligible thickness, like a sheet of paper
what are the modelling assumptions of lamina
mass is distributed across a flat surface
what does the uniform body model mean
mass is distributed evenly
what are the modelling assumptions of uniform body
mass of the object is concentrated at a single point in the geometrical centre if the body- the centre of mass
what does the light object model mean
mass of the object is small compared to other masses, like a string or a pulley
what are the modelling assumptions of light object
-tension at the same at both ends of a light string
-treat object as having zero mass
what does the inextensible string model mean
A string that does not stretch under load
what are the modelling assumptions of inextensible string
- acceleration is the same in objects connected by a taut inextensible string
smooth surface modelling assumptions
- assume there is no friction between the surface and any object on it
what does the rough surface model mean
if a surface is not smooth, it is rough
rough surface modelling assumptions
- objects in contact with the surface experience a frictional force if they are moving or are acted on by a force.
Wire model meaning
Rigid thin length of metal.
Smooth and light pulley model meaning
all pulleys you consider will be smooth and light.
wire model assumptions
treated as one-dimensional
Smooth and light pulley model assumptions
pulley has no mass
tension is the same on either side of the pulley
Bead model meaning
Particle with a hole in it for threading on a wire or string.
Bead modelling assumptions
moves freely along a wire or string
tension is the same on either side of the bead
Peg model meaning
A support from which a body can be suspended or rested
peg model assumptions
dimensionless and fixed
can be rough or smooth as specified in question
air resistance model meaning
Resistance experienced as an object moves through the air.
air resistance model assumptions
usually modelled as being negligible
Gravity model meaning
Force of attraction between all objects. Acceleration due
g = 9.8 ms?
to gravity is denoted by g
gravity modelling assmuption
assume that all objects with mass are attracted towards the Earth
Earth’s gravity is uniform and acts vertically downwards
g is constant and is taken as 9.8 m s-‘, unless otherwise stated in the question
