What are the assumptions about modelling a particle?
- the mass is concentrated at a single point
- rotational forces and air resistance are ignored
What are the assumptions about modelling a rod?
- no thickness
- the mass is concentrated along a single line
- rigid (does not bend)
What are the assumptions about modelling a lamina?
- mass is distributed across a flat surface
What are the assumptions about modelling a uniform body?
- the mass is concentrated at a single point at the centre of the body - the centre of mass
What are the assumptions about modelling a light object?
- has zero mass
- tension the same at both ends of the string
What are the assumptions about modelling an inextensible string?
- acceleration is the same in objects connected by a taut inextensible string
What are the assumptions about modelling a smooth surface?
- there is no friction between the surface and any object on it
What are the assumptions about modelling a rough surface?
- objects in contact with the surface experience a frictional force if they are moving or are acted on by a force
What are the assumptions about modelling a wire?
- treated as one dimensional
What are the assumptions about modelling a smooth and light pulley?
- pulley has no mass
- tension is the same on either side of the pulley
What are the assumptions about modelling a bead?
- moves freely along a wire or string
- tension is the same on either side of the bead
What are the assumptions about modelling a peg?
- no dimensions and fixed
- can be rough or smooth - is specified in question
What are the assumptions about modelling air resistance?
- modelled as negligible
What are the assumptions about modelling gravity?
- 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 ms^-1, unless otherwise stated in the question
