Physics
posted by Reese on .
Halley’s comet orbits the Sun with a period of 76.2 years.
a) Find the semimajor axis of the orbit of Halley’s comet in astronomical units (1 AU is equal to the semimajor axis of the Earth’s orbit

There is a simple form of Kepler's Third law for objects orbiting the sun.
If the period P is in years and the semimajor axis a is in a.u.,
P^2 = a^3
You know that P = 76.2 yr
Solve for a