What is modelling in Mechanics?

• Mechanics uses?modelling?to solve problems in real life situations
• We use?assumptions?to simplify real life problems in order to turn them into equations or graphs that can be solved
• We will sometimes need to?criticise?or?refine our assumptions?to improve the model

Modelling Assumptions in Mechanics:

• There are many different?modelling assumptions?that can be made when dealing with?real life situations
• Different assumptions will be needed for different models
• The assumptions you make will affect the calculations in each problem differently

What types of modelling assumptions are there?

• Gravity?is constant and vertical
• Air resistance?is usually modelled as?negligible?and can be ignored
• A?smooth?surface has no?friction
• A?rough?surface has a?frictional force?between the surface and any object that makes contact with it
• A?particle?has?negligible?dimensions, therefore forces will all act on a particle at the same point
• A?rod?or a?beam?should be treated as a long, rigid particle
• A?uniform?object’s?mass?is distributed evenly
• A?light?object has zero?mass
• An?inextensible?object cannot be stretched

a) A and B are both particles.

b) The string is light.

c) The string is inextensible.

d) The pulley is smooth.

e) The surface A is moving along is smooth.