1
Q
Particle - dimensions of the object are negligible
A
- mass of the object is concentrated at a single point
- rotational forces and air resistance can be ignored
2
Q
Rod- all dimensions but one are negligible (e.g. beam)
A
- No thickness
- Mass is concentrated along a line
- Rigid (doesn’t bend)
3
Q
Lamina - object with area but negligible thickness, like a sheet of paper
A
- Mass is distributed across a flat surface
4
Q
Uniform body - mass is distributed evenly
A
- Mass of the object is concentrated at the centre of mass
5
Q
Light object - has a smaller mass compared to other objects (e.g. string)
A
- Treat object as having 0 mass
- Tension is the same at both ends of a light string
6
Q
Inextensible string - doesn’t stretch under load
A
- Acceleration is the same in objects connected by a taut inextensible string
7
Q
Smooth object
A
- Assume there is no friction between the surface and any objects on it
8
Q
Rough surface
A
- Objects in contact with the surface experience a frictional force if they are moving or are acted on by a force.
9
Q
Wire - rigid thin length of metal
A
- Treated as one dimensional
10
Q
Smooth/ light pulley
A
- Pulley has no mass
- Tension is the same on either side of the pulley
11
Q
Bead- particle with a hole in it for threading on a wire
A
- Moves freely along a wire/string
- Tension is the same on either side of the bead
12
Q
Peg- a support from which a body can be suspended
A
- Dimensionless and fixed
- Can be rough or smooth as specified in question
13
Q
Air resistance - resistance experienced as an object moves through the air
A
- Usually modelled as being negligible
14
Q
Gravity - force of attraction between all objects.
A
- Assume that all objects with mass are attracted towards the Earth
- Earth’s gravity is uniform and acts vertically downwards.
- Acceleration due to gravity is ‘g’ (9.8ms-2). It is constant.
Mechanics
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