Mechanics - Models

Question 1

What is the particle model?

Answer 1

Dimension are negligeble

Question 2

What is the rod model?

Answer 2

1 dimension, like a pole or beam

Question 3

What is the lamina model?

Answer 3

2 dimensions with area, like paper

Question 4

What is the uniform body model?

Answer 4

Mass is evenly distributed

Question 5

What is the light object model?

Answer 5

Mass is small in comparison to other objects (like a string vs a hanging mass)

Question 6

What is the inextensible string model?

Answer 6

A string that does not stretch/extend under load

Question 7

What does the smooth surface model assume?

Answer 7

No friction between object and surface

Question 8

What does the rough surface model assume?

Answer 8

Objects in contact with surface experience frictional force if they are moving or acted on by a force

Question 9

What is the wire model?

Answer 9

Rigid thin length of metal, 1 dimension like rod model

Question 10

What is the smooth and light pulley model?

Answer 10

All pulleys considered in situation will be smooth and light

Question 11

What is the bead model?

Answer 11

Particle with hole in for threading on a wire or string

Question 12

What is the peg model?

Answer 12

A support from which a body can be suspended or rested

Question 13

What is the air resistance model?

Answer 13

Resistance experienced as an object moves through the air

Question 14

What is the gravity model?

Answer 14

Force of attraction between all objects, where acceleration due to gravity = g

Question 15

What is assumed by the particle model?

Answer 15

> Mass of object is concentrated at a single point

> Rotational forces and air resistance can be ignored

Question 16

What is assumed by the rod model?

Answer 16

> Mass is concentrated along a line
No thickness
Rigid (does not bend or buckle)

Question 17

What is assumed by the lamina model?

Answer 17

Mass is distributed evenly across a flat surface

Question 18

What is assumed by the uniform body model?

Answer 18

Mass is concentrated at a single point at the geometrical centre of the body - the centre of mass

Question 19

What is assumed by the light object model?

Answer 19

> Objects are treated as having zero mass

> Tension is the same at both ends of a light string

Question 20

What is assumed by the inextensible string model?

Answer 20

> Acceleration is the same in objects connected by a taut inextensible string

Question 21

What is assumed by the smooth and light pulley model?

Answer 21

> The pulley has no mass

> The tension is the same on either side of the pulley

Question 22

What is assumed by the bead model?

Answer 22

> Moves freely along a wire or string

> The tension is the same on either side of the bead

Question 23

What is assumed by the peg model?

Answer 23

> Dimensionless and fixed

> Can be rough or smooth (as specified in question)

Question 24

What is assumed by the air resistance model?

Answer 24

> Usually modelled as being negligible

Question 25

What is assumed by the gravity model?

Answer 25

> Assume that all objects with mass are attracted towards the Earth
Earth’s gravity is uniform and acts downwards
g = 9.8 ms⁻¹ unless stated otherwise