modelling assumptions

Question 1

particle

Answer 1

• dimensions of the objects are negligible (unimportant), all mass is concentrated on a single point

-rotational forced & air resistance can be ignored

Question 2

rod

Answer 2

one dimension

MA:
-mass is along a concentrated line
-no thickness
-rigid (does not bend)

Question 3

lamina

Answer 3

object with area but unimportant thickness

MA:
mass distributed across a flat surface

Question 4

uniform body

Answer 4

mass is distributed evenly.

MA:
mass is concentrated on the centre

Question 5

light object

Answer 5

mass of the object is small compared to other masses

MA:
treat object as it has zero mass

Question 6

inextensible string

Answer 6

a string that does not stretch under load

MA:
acceleration is the same in objects connected by a taut inextensible string

Question 7

smooth surface

Answer 7

no friction between surface and object

Question 8

rough surface

Answer 8

if not smooth, it is rough.

MA:
objects in contact with surface has frictional force if moving or acted on by a force

Question 9

wire

Answer 9

rigid thin length of metal

MA:
treat as one dimensional

Question 10

smooth and light pulley

Answer 10

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

Question 11

bead

Answer 11

particle with a hole in it for threading on a wire or a string

-tension is same either side of the bead
-moves freely along the wire and string

Question 12

peg

Answer 12

support from which a body can be suspended or rested

-dimensionless and fixed

Question 13

air resistance

Answer 13

resistance experienced as an object moves through the air