The document summarizes how the Coriolis force causes objects on the surface of the Earth to move in circles. It shows that the radius of the circular path is given by r = v/(2ωcosθ), where v is the object's velocity, ω is the Earth's rotation rate, and θ is the co-latitude. The frequency of circular motion is 2ωcosθ. For example, near the equator where θ is close to π/2, r becomes very large and the frequency approaches 0, while near the north pole, r is on the order of 10 km for an object moving at 1 m/s.