Two planets travel in circular orbits about a star at radii of ra = 2r and rb = r, respectively. What is the ratio of their periods ta/tb?.

If you were to drop a rock from a tall building, assuming that it had not yet hit the ground, and neglecting air resistance. what is its vertical displacement (in m) after 6 s?

An airplane flies eastward and always accelerates at a constant rate. at one position along its path it has a velocity of 34.3 m/s, it then flies a further distance of 40100 m and afterwards its velocity is 47.5 m/s. find the airplane\'s acceleration and calculate how much time elapses while the airplane covers those 40100 m.

An object moves from position +34m to the position -15m in 15 seconds. what is the total displacement? what is the total velocity?