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
What is a wire?
Rigid thin length of metal
What are the modelling assumptions of a wire?
Treated as one dimensional
What is a smooth and light pulley?
All pulleys you consider will be smooth and light
What are the modelling assumptions of a smooth and light pulley?
- Pulley has no mass
- Tension is the same on either side of the pulley
What is a bead?
Particle with a hole in to for threading on a wire or string
What are the modelling assumptions for a bead?
- Moves freely along a wire or string
- Tension is the same either side of the bead
What is a peg?
A support from which a body can be suspended or resteed
What are a modelling assumptions for a peg?
- Dimensions are fixed
- Can be rough or smooth as specified in question
What is air resistance?
Resistance experienced as an object moves through the air
