Long description

This is a diagram of a circular earth with the following features: a vertical line through the centre, labelled N at the top, S at the bottom; a horizontal line through the centre, the equator; omega shows the spinning clockwise (when viewed from above the N pole); a red circle is at a point on the top right of the circle; a velocity vector by the red dot, u, is pointed down to the right (moving southwards) at a tangent to the circle; another vector u subscript s, is a horizontal arrow pointing to the right from the red circle; a vertical line linking the tip of the u subscript s vector with the tip of the u vector shows that u makes an angle theta to the vertical (here about 45 degrees).