Cambridge O Level Physics · Syllabus 5054 · Space Physics
Orbital Period
What is Orbital Period?
The orbital period T is the time taken for one complete orbit. For calculations in SI units it must be converted into seconds: multiply days by 86 400 or hours by 3600.
This definition is part of the Space Physics chapter in Cambridge O Level Physics.
Questions students ask about Orbital Period
How do you calculate a planet's average orbital speed?
Average orbital speed is the circumference of the orbit divided by the orbital period, \(v = 2\pi r/T\), where \(r\) is the average radius of the orbit measured from the centre of the central body and \(T\) is the time for one complete orbit. The period must be in seconds for the SI unit of speed, so convert days by multiplying by 86 400 or hours by multiplying by 3600 before substituting.
Last reviewed Syllabus 2026-2028