Intro To Mechanics Flashcards
Modelling assumption
Particle
Mass of object is concentrated at a single point
Rotational forces and air resistance can be ignored
Rod
Mass is concentrated along a line
No thickness
Rigid (does not bend)
Lamina
Mass is distributed across a flat surface
Uniform body
Mass of object is concentrated at a single point - the centre of mass
Light Object
Treat object as having zero mass
Tension the same at both ends of a light string
inextensible String
Acceleration is equal in all objects connected by this type of string
Particle
Mass of object is concentrated at a single point
Rotational forces and air resistance can be ignored
Rod
Mass is concentrated along a line
No thickness
Rigid (does not bend)
Lamina
Mass is distributed across a flat surface
Uniform body
•
Mass of object is concentrated at a single point - the centre of mass
Light Object
Treat object as having zero mass
Tension the same at both ends of a light string
nextensible String
• Acceleration is the same in objects connected by a taut inextensible string
Smooth Surface
Assume there is no friction between the surface and any object on it
Rough Surface
Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force
Wire
Treated as one-dimensional
Smooth and Light Pulley
Pulley has no mass
Tension is the same on either side of the pulley
Bead
Moves freely along a wire or string
Tension is the same on either side of the bead
Peg
Dimensionless and fixed
Can be rough or smooth as specified in question
Air Resistance
Usually modelled as being negligible
Gravity
Assume that all objects with mass are attracted towards the Earth
Earths’ gravity is uniform and acts vertically downwards g is constant and is taken as 9.8 ms-2 unless otherwise stated. Acceleration is the same in objects connected by a taut inextensible string
Smooth Surface
Assume there is no friction between the surface and any object on it
Rough Surface
Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force
Wire
Treated as one-dimensional
Smooth and Light Pulley
Pulley has no mass
Tension is the same on either side of the pulley
Bead
Moves freely along a wire or string
Tension is the same on either side of the bead
Peg
Dimensionless and fixed
Can be rough or smooth as specified in question
Air Resistance
Usually modelled as being negligible
Gravity
Assume that all objects with mass are attracted towards the Earth
Earths’ gravity is uniform and acts vertically downwards g is constant and is taken as 9.8 ms-2 unless otherwise stated.
