ABSTRACT
If a quantity y depends on and varies with a quantity x then the rate of change of y with respect to x is
dy dx
Thus, for example, the rate of change of pressure p with height h is
dp dh
A rate of change with respect to time is usually just called ‘the rate of change’, the ‘with respect to time’ being assumed. Thus, for example, a rate of change of current, i, is
di dt
and a rate of change of temperature, θ ,
is dθ dt
, and so on.
