Light
0 mass
Static
Stays still
Rough
Friction working against the object
Smooth
No friction to consider
Rigid
Can not be bent
Thin
Don’t need to worry about thickness
Particle
Air resistance no effect
Plane
Flat surface
Lamina
2d object
Beam or rod
Rigid can’t bend
W
Wire
Rigid
Inextensible - can’t stretch
String
Inextensible
Thin
Peg
Rest something on
Pulley
Disc hang strings wrapped around pulley