Modelling Assumptions
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
Worked Example
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.
Exam Tip
- Make sure you fully understand the definitions of all the words in this section so that you can be clear about what your exam question is asking of you.
