## Period Derivative

• The period derivative is the rate at which an object's orbital or rotation period P is changing - ie the instaneous change in period divided by the change in time. In calculus terms this is simply dP/dt and is often expressed as a dimensionless quantity.

Sometimes physicists use the simple dot above a quantity to represent the derivative with respect to time t, so the period derivative dP/dt is often called P-dot, ie:

here the subscripts 0 and f refer to the initial and final conditions respectively.

Applications