Mechanics

Question 1

Particle

Answer 1

Dimensions of object are negligible so
- Ignore air resistance and rotational forces
- mass is concentrated at single point

Question 2

Rod

Answer 2

All dimensions but one are negligible so
- Mass concentrated along a line
- No thickness
- Rigid

Question 3

Lamina

Answer 3

Objet with thickness but negligible thickness so
- Mass is distributed across flat surface

Question 4

Uniform body

Answer 4

Mass is evenly distributed so
- Centre of mass is at geometrical centre of body

Question 5

Light object

Answer 5

Mass is small compared to other objects so
- Mass treated as 0
- Tension same at both ends of light string

Question 6

Inextensible string

Answer 6

String does not stretch under load
- Acceleration of objects connected by taut string is same

Question 7

Smooth surface

Answer 7

Assume no friction between surface and any object on it

Question 8

Rough surface

Answer 8

There is friction between surface and object on it

Question 9

Wire

Answer 9

Rigid, thin length of material
- treated is 1D

Question 10

Smooth and light pulley

Answer 10

All pulleys will be like this
- Pulley has no mass
- Tension is same on both sides

Question 11

Bead

Answer 11

Particle with hole in it for threading string/wire
- Moves freely along wire or string
- Tension on both sides of bead is same

Question 12

Air resistance

Answer 12

Resistance experienced as an object moves through the air - usually modelled as negligible

Question 13

Gravity

Answer 13

Force of attraction between all objects
- Assume all objects with mass are attracted towards Earth
- Assume g is uniform and acts vertically downwards