The planet Neptune has an orbital radiu around the sun of about 4.50 * 10^12m. What are its period and its orbital speed?

Answer 1

Use Kepler's third law. If R is in a.u. and the period T is in years,

T^2 = R^3
(for solar sytem planets only)

For the velocity , use
v = 2*pi*R/T
and express T in seconds and R in meters