Studied by 2 peopleParticle - DImensions of the object are negligible
mass of the object is concentrated at a single point
rotational forces and air resistance can be ignored
Rod - All dimensions but one are negligible, like a pole or beam
mass is concentrated along a line
no thickness
rigis (does not bend or buckle)
Lamina - Object with area but negligible thickness, like a sheet of paper
mass is distributed across a flat surface
Uniform body - Mass is distributed evenly
mass of the object is concentrated at a single point at the geometrical centre of the body - the centre of mass
Light object - Mass of the object is small compared to other masses, like a string or a pulley
treat object as having zero mass
tension the same at both ends of a light string
Inextensible string - A string that does not stretch under load
acceleration is the same in objects connected by a taut inextensible string
Smooth surface
assume that there is no friction between the surface and any object on it
Wire - Rigid thin length of metal
treated as one-dimensional
Smooth and light pulley - all pulleys you consider will be smooth and light
pulley has no mass
tension is the same on either side of the pulley
Bead - Particle with a hole in it for threading on a wire or string
moves freely along a wire or string
tension is the same on either side of the bead
Peg - A support from which a body can be suspended or rested
dimensionless and fixed
can be rough or smooth as specified in question
Air resistance - Resistance experienced as an object moves through the air
usually modelled as bring negligible
Gravity - Force of attraction between all objects. Acceleration due to gravity is donoted by g
assume that all objects with madd are attracted towards the Earth
Earth’s gravity is uniform and acts vertically downwards
g is a constant and is taken as 9.8 m s^-2 unless otherwise stated in the question
Note
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