Your spaceship lands on an unknown planet. To determine the characteristics of this planet, you drop a 1.40 kg wrench from 5.50 m above the ground and measure that it hits the ground 0.811 s later. You also do enough surveying to determine that the circumference of the planet is 6.20×10^4 km.
(a) What is the mass of the planet, in kilograms?
(b) Express the planet's mass in terms of the earth's mass.