Coriolis path calculator
Start with eastward motion in a horizontal rotating frame. Follow the path under the Coriolis term at one fixed latitude, with speed conserved throughout the track.
After 300 s, the eastward-starting track reaches 2,999.414 m east and -51.357 m north of its start. Speed stays 10 m/s; the Coriolis term changes its direction.
Read this calculation
f = 2Ω sin φ; du/dt = f v; dv/dt = −f u
Positive north and east define the plotted axes. An initially eastward track bends south in the northern hemisphere and north in the southern hemisphere. The equatorial case stays straight.
This f-plane scenario holds latitude fixed and includes only the horizontal Coriolis term. Wind, drag, pressure gradients, terrain and projectile height are separate forces or motions; enter a short local track when comparing a real measurement.
For a drain-scale comparison, set latitude 45°, speed 0.1 m/s and time 10 s. The isolated rotating-frame path bends about 0.00052 m sideways while moving about 1 m. A leftover side speed of only 0.01 m/s moves 0.1 m in that interval, roughly 190 times farther. Container shape, plug removal and residual swirl can dominate an ordinary sink; a controlled rotation experiment has to reduce those disturbances.