8 Summary of the important points.
- Statics is the study of bodies that are either at rest or moving with a constant velocity.
- A “particle” is an object whose size can be neglected, but it has a mass. If it does not deform under pressure it is called a “rigid body”.
- If the forces can be considered to act at a point on a body, they are called concentrated forces.
- Newton’s three laws of motion need to be applied. You should have them memorized. Have them written down in a convenient place. You want to start developing your own reference or “cheat sheet” of equations and principles.
- Mass is a measure of inertia. It does not change as it moves from one location to another and that includes from the Earth to the Moon. Weight is the name we give to the force of attraction between an object with mass and the planet. In this course we are normally talking about the surface of the Earth, but we will spend a small amount of time analyzing satellites in orbit around the Earth. The weight of an object changes depending on the distance between it and the centre of the Earth.
- In the SI or Metric System, the unit of force is a newton, symbol N. It is a unit derived from the base units of metre, second and kilogram.
- In the US Customary or Imperial System, the unit of force is the pound, symbol lb. The foot, second and pound are base units and the unit of mass is called the slug.
- Engineering notation is when the metric prefixes n, μ (pronounced mu), m, k, M, G, T are used to designate small and large numerical quantities. For example km, which means kilometre or one-thousand metres. You should have these memorized or keep them handy.
- Numerical calculations should be done with many significant figures, and should be rounded off to only three significant figures at the end.
- You can check that you have done the algebraic manipulations of the equations by checking that the units used are consistent throughout.