Modelling In Mechanics Flashcards
model- particle
Dimensions of the object are negligible
Particle modelling assumptions
- mass of object is concentrated at a single point
- rotational forces and air resistance can be ignored
Model - rod
All dimensions but one are negligible, like a pole or a beam
Rod modelling assumptions
- mass is concentrated along a line
- no thickness
- rigid(does not bend or buckle)
Model - lamina
Object with area but negligible thickness, like a sheet of paper
Lamina modelling assumptions
Mass is distributed across a flat surface
Model- uniform body
Mass is distributed evenly
Uniform body modelling assumptions
- mass of the object is concentrated at a single point at the geometrical centre of the body - the centre of mass
Light object model
Mass of the object is small compared to other masses, like a string or a pulley
Light object modelling assumptions
- treat object as having zero mass
- tension the same at both ends of a light string
Inextensible string model
A string that does not stretch under load
Inextensible string modelling assumptions
Acceleration is the same in objects connected by a taut inextensible string
Smooth surface model assumption
Assume that there is no friction between the surface and any object on it
Rough surface model
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 re moving or are acted on by a force
Wire model
Rigid thin length of metal
Wire model assumptions
Treated as one-dimensional
Smooth and light pulley model
All pulleys you consider will be smooth and light
Smooth and light pulley modelling assumptions
- pulley has no mass
- tension is the same on either side of the pulley
Bead model
Particle with a hole in it for threading on a wire or string
Bead model assumptions
-moves freely along a wire or string
-tension is the same on either side of the bead
Peg model
A support from which a body can be suspended or rested
Modelling assumptions
- dimensionless and fixed
- can be rough or smooth as specified in the question
Air resistance model
Resistance experienced as an object moves through the air
Air resistance modelling assumptions
Usually modelled as being negligible
Gravity model
Force of attraction between all objects
Acceleration due to gravity being denoted by g
Gravity modelling assumptions
-assume that all objects with mass are attracted towards the earth
- Earth’s gravity is uniform and vertically downwards
- g is constant and is taken as 9.8ms^-2 , unless otherwise stated in the question
