* So it appears that there are 3 kinds of dimensions: Basic, Derived and Spatial Dimensions.In physics and science, dimensional analysis is a tool to find or check relations among physical quantities by using their dimensions. The dimension of a physical quantity is the combination of the basic physical dimensions (usually mass, length, time, electric charge, and temperature) which describe it; for example, speed has the dimension length / time, and may be measured in meters per second, miles per hour, or other units. Dimensional analysis is based on the fact that a physical law must be independent of the units used to measure the physical variables. A straightforward practical consequence is that any meaningful equation (and any inequality and inequation) must have the same dimensions in the left and right sides. Checking this is the basic way of performing dimensional analysis.
1st, There are 5 basic dimensions: Mass, Length, Time, Charge, Temperature.
2nd, There are many derived dimensions: Speed, Acceleration, Force, Pressure, Momentum, Energy, etc.
- Any product or ratio of two or more basic dimensions is called a derived dimension. Speed = Length/Time. Acceleration = Speed/Time. Force = Mass x Acceleration. Etc. I think Einstein said Speed x Time = Length, but as a fourth dimension. But it seems better to call it a derived dimension, instead of a basic one.
3rd, There are 3 basic spatial dimensions, each perpendicular to the other two: Length, Width, Height.
- There are 2 derived spatial dimensions: Length x Length = Two-dimensional Area; Length x Length x Length = Three-dimensional Volume.
* Beware!
- Some say that temperature, charge and even mass may be derived, rather than basic, dimensions. They may be derived from length and time, as Dewey Larsen claimed. In that case, there are just 2 basic dimensions: Length and Time.
* Any Questions?