Mechanics - Modelling Assumptions Flashcards
What is a particle?
Dimensions of the object are negligible
What are the modelling assumptions for a particle?
- Mass of object is concentrated at a single point
- Rotational forces + air resistance can be ignored
What is a rod?
All dimensions but one are negligible, like a pole or a beam
What are the modelling assumptions for a rod?
- Mass is concentrated along a line
- No thickness
- Rigid (does not bend or buckle)
What is a lamina?
Object with an area but negligible thickness i.e. a sheet of paper
What are the modelling assumptions for lamina?
Mass is distributed across a flat surfce
What is a uniform body?
Mass is distributed evenly
What are the modelling assumptions for a uniform body?
Mass of the object is concentrated at a single at the geometrical centre on the body - the centre of mass
What is a light object?
Mass of the object is small compared to other masses, like a string or a pulley
What are the modelling assumptions for a light object?
- Treat object as having zero mass
- Tension the same at both ends of the light string
What is an inextensible string?
A string that does not stretch under a load
What are the modelling assumptions for an inextensible string?
Acceleration is the same in objects connected by a taut inextensible string
What are the modelling assumptions for a smooth surface?
Assume that there is no friction between the surface and any objects on it
What is a rough surface?
If a surface is not smooth it is rough
What are the modelling assumptions of a rough surface?
Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force
