In: Physics
Since force is m*a, it has units of kg m/s^2 . Energy has units of kg m^2/s^2. Thus it appears that by lazy dimensional analysis that a force times a distance will have units of energy. This turns out to be the formula to calculate work. Note also that kg m^2/s^2 looks like mv^2. Here if we use dimensional analysis, we would *almost* find the formula for kinetic energy. We'd be off by a factor of two since KE=1/2 mv^2. Note that this would still be useful for estimation (such as we did the first few weeks).
Many physical quantities are unitless and dimension less..(Numbers , trigonometric function, exponential functions, etc)
There are some quantities having both dimension and unit. Some have unit but no dimension. But if a quantity has no unit then ,it must not have a dimension.