Modelling assumptions

Question 1

Modelling assumptions

Answer 1

Air resistance
Lamina
Rod
Tension is the same at both ends of a light spring. Here, the mass is very small(regarded as zero).
The surface is smooth
Wire
The surface is rough
Particle
Uniform body
Gravity
Inextensible

Question 2

Air resistance

Answer 2

The friction an object experiences as it moves through space

Question 3

Lamina

Answer 3

An object with two dimensions(length and width), such as a sheet of metal. Its mass is evenly distributed across a flat surface.

Question 4

Rod

Answer 4

An object with one dimension(length), such as a pole or a beam. Its mass is distributed along a straight line. It is rigid(does not bend or buckle).

Question 5

Smooth surface

Answer 5

This assumes there’s no friction between this surface and an object.

Question 6

Wire

Answer 6

A rigid, thin length of metal, treated as one dimensional, either smooth or rough

Question 7

Rough surface

Answer 7

This takes into account friction on surfaces

Question 8

Particles

Answer 8

Where dimensions of the object are negligible/unimportant. Its mass is concentrated at a single point. Air resistance and rotational forces can be ignored.

Question 9

Uniform body

Answer 9

Its mass is evenly distributed. Its mass is concentrated at the geometrical centre of the body(centre of mass).

Question 10

Gravity

Answer 10

The force of attraction to the Earth, measured at 9.8m/s2. It is uniform and acts vertically downwards

Question 11

Inextensible

Answer 11

When an object does not stretch under a load. Acceleration is constant in objects connected by a taut inextensible string.

Question 12

One improvement to model of motion to make the model more realistic

Answer 12

As velocity increases, rate of acceleration decreases

Question 13

Assumption for air resistance in model

Answer 13

Usually ignored

Question 14

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

Answer 14

Moves freely along a wire or string
Tension is the same on either side of the bead

Question 15

Assumption for beam- like a pole

Answer 15

Ignore its thickness.
its mass is concentrated along a line.
It doesn’t bend

Question 16

Assumptipn for gravity

Answer 16

It’s uniform, acts vertically downwards and is about 9.8m/s2 unless stated otherwise.

Question 17

Assumption for inextensible

Answer 17

It does not stretch

Question 18

Assumption for lamina

Answer 18

It has an area, but ignore its thickness

Question 19

Assumption for light object

Answer 19

Ignore its mass

Question 20

Assumption for particle

Answer 20

Assume it has no mass or dimensions

Question 21

Assumption for peg - a support from which something can hang

Answer 21

Ignore dimensions

Question 22

Assumption for Rod

Answer 22

Ignore its thickness. Its mass is concentrated along a line. It doesn’t bend

Question 23

Assumption for Smooth

Answer 23

Ignore any friction

Question 24

Assumption for Uniform

Answer 24

Its mass is either evenly spread throughout the body or is concentrated at a single point

Question 25

Assumption for wire

Answer 25

Ignore thickness. Its mass is concentrated along a line. It does not bend

Question 26

Realistic velocity time graph

Answer 26

Rate of acceleration decreases as velocity increases