Modelling asdumptions

• When the model is a particle, all dimensions of the object are negligable
• Particle assumptions:

  --> mass of object is concentrated at a single point

  --> rotational forces and air resistance can be ignored
• When the model is a rod, all dimensions but one is negligable
• Rod assumptions:

  --> mass is concentrated along a line

  --> no thickness

  --> rigid
• When the model is lamina, the object with area but negligible thickness
• Lamina assumption:

  --> massi is distributed across flat surface
• When it's a uniform body, mass is evenly distributed
• Uniform body assumptions:

  ---> mass of object is concentrated at a single point at the geometrical centre of the body (centre of mass)
• Light object means mass of object is small compared to other masses, like a string or a pulley
• Light object assumptions:

  --> treat object as having zero mass

  --> tension the same at both ends of a light string
• Inextensible string means that a string does not stretch under load
• Inextensibke string assumptions:

  --> acceleration is the same in objects connected by taut Inextensibke string
• Smooth surface assumption:

  --> no friction between surface and any object on it
• Rough surface assumptions:

  --> objects in contact with the surface experience a frictional force if they are moving or are acted on
• Wire is a rigid thin length of metal
• Wire is treated as one dimensional
• Smooth and light pulley - all pulleys you consider will be smooth and light
• Pulley assumotions:

  --> pulley has no mass

  --> tension is the same on either side of the pulley
• Bead is a particles with a hole in it for threading a wire or string
• Bead assumptuions:

  --> moves freely along wire or string

  --> tension is the same on either side of the bead
• Peg is a support from which a body can be suspended or rested
• Peg assumptions:

  --> dimensionless

  --> fixed

  --> can be rough or smooth
• Air resistance is resistance experienced as an object moves through air
• Air resistance assumptions:

  --> usually modelled as negligible
• Gravity is a force of attraction between all objects.
• Gravity assumptions:

  --> assume all objects with mass are attracted to earth

  --> earth's gravity is uniformband acts vertically down

  --> g us constant and taken as 9.8