# Models and modelling assumptions

Model
Modelling Assumption
1 of 15
Particle - dimensions are negligible
Rotational forces and air resistance are ignored. The mass is concentrated in one place
2 of 15
Rod - only 1 dimension is important (rod or beam)
No thickness. Mass in concetrated along line. Rigid
3 of 15
Lamina - area but negigble thickness (sheet of paper)
Mass distributed across surface
4 of 15
Uniform body - mass is distributed evenly
Mass is concetrated at a single point at the centre (centre of mass)
5 of 15
Light Object - mass is small compared to other objects (string, pulley)
Object has ZERO mass. Tension is equal both ends of a light string.
6 of 15
Inextensible sting - a string that doesn't stretch under a load.
The ACCELERATION is the same in both objects connected by a taut, inextensible string.
7 of 15
Smooth surface
Friction between object and surface is ingnored. (assume there isn't any)
8 of 15
Rough Surface
There IS friction between the surface and objects on it when they are moving.
9 of 15
Wire - rigid thin length metal
Treated as 1 dimensional
10 of 15
Smooth and light pulley - ALL pulleys you consider will be like this.
Pulley has no mass. Tension is the same on either side of the pulley.
11 of 15
Bead - particle with a hole on for threading on a string or wire
Moves freely along the wire. Tension is the same on either side of the bead.
12 of 15
Peg - a support which a body can be rested or suspended from
Dimensionless and fixed. Rough or smooth (said in question)
13 of 15
Air Resistance
Normally negibible
14 of 15
Gravity - force of attraction between all objects. Acceleration of objects due to gravity is "g"
"g" is constant and 9.8 m/s^2. All objects with mass are attracted to Earth. Earth's gravity is uniform and acts verically downwards.
15 of 15

## Other cards in this set

### Card 2

#### Front

Rotational forces and air resistance are ignored. The mass is concentrated in one place

#### Back

Particle - dimensions are negligible

### Card 3

#### Front

No thickness. Mass in concetrated along line. Rigid

### Card 4

#### Front

Mass distributed across surface

### Card 5

#### Front

Mass is concetrated at a single point at the centre (centre of mass)