Modelling assumptions Flashcards
(16 cards)
Particle
Negligible dimensions. Mass concentrated at a single point, ignore rotational forces and air resistance
Rod
All dimensions but one negligible. Mass concentrated along a line, no thickness, rigid
Lamina
Object with area but negligible thickness. Mass distributed across a flat surface
Uniform body
Mass distributed evenly. Mass concentrated at a single point at the geometrical centre of the body - the centre of mass
Light object
Mass of object small compared to other masses. Treat as if zero mass, same tension through a light string
Inextensible string
Doesn’t stretch under load. Same acceleration if a taut inextensible string connects
Smooth surface
No friction between surface and objects
Rough surface
Objects on the surface experience frictional force if acted on by a force
Wire
Rigid thin length of metal. One-dimensional
Smooth and light pulley
All of them. Pulley has no mass, same tension either side
Bead
Particle with a hole in it to thread on a wire/string. Moves freely along a wire/string, same tension either side of string
Peg
A support from which a body can be suspended or rested. Dimensionless and fixed, can be rough or smooth
Air resistance
Resistance experienced as an object moves through the air. Usually modelled as negligible
Gravity
Force of attraction between all objects. Assume all objects with mass attracted to Earth, uniform and acts vertically downwards, constant and taken as 9.8
Why same tension
Light object/bead threaded on a wire/string, smooth and light pulley
Why same acceleration
Objects connected by a taut inextensible string
