Mechanics 1

-mass of object concentrated at single point
-rotational forces and air resustance can be ignored

-mass concentrated along a line
-no thickness
-rigid (no bending or buckling)

-mass distributed across flat surface

-mass of object concentrated at single point at geometrical centre of body (centre of mass)

-treat as having 0 mass
-tension same at both ends of light string

-acceleration same in objects connected by taut inextensible string

-assume no friction between surface and object on it

-objects in contact with it experience frictional force if acted on by force

treated as 1 dimensional

-pulley has no mass
-tension is same either side of pulley

-moves freely along wire or string
-tension same on either siide of bead

-dimensionless and fixed
-can be rough or smooth as specified

-usually modelled as being negligible

-all objects with mass attracted to earth
-earth’s gravity is uniform and acts vertically downwards
-g is constant and is 9.8m/s2

kg

m

s

force acting vertically downwards due to gravity

force acting perpendicular to surface when an object is in contact with surface

force opposing motion between 2 rough surfaces

force acting on an object pulled by a string

force acting on object if object pushed using light rod

upward force on body that allows it to float or rise when submerged in liquid

force that opposes motion in air

quantity which has both magnitude and direction

quantity with only magnitude