What caused wind to deflect towards left in Southern Hemisphere?

Question

UnlockIAS · Accepted Answer

Correct — D, Coriolis force. Because the Earth rotates on its axis, any freely moving object — including wind — appears to be deflected from a straight path. This apparent deflection is the Coriolis force (Ferrel's Law): winds are deflected to the RIGHT in the Northern Hemisphere and to the LEFT in the Southern Hemisphere. It is zero at the equator and maximum at the poles, and it acts at right angles to wind direction. Hence the leftward deflection of Southern-Hemisphere winds is caused by the Coriolis force.

Why the other options are wrong — (a) Temperature differences create the pressure differences that set winds in motion, but they do not cause the sideways (left/right) deflection — that comes from Earth's rotation via the Coriolis effect.  (b) The pressure-gradient force pushes air from high to low pressure (the wind's initial direction); the deflection to the left/right is the Coriolis force, not pressure itself.  (c) Earth's magnetic field deflects charged particles, not neutral air masses; it plays no role in deflecting winds.

Concept: The Coriolis force is an apparent (inertial) force arising from Earth's rotation. It deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Its magnitude equals 2 x omega x v x sin(latitude) — so it grows with wind speed and latitude, being zero at the equator (sin 0 = 0) and maximum at the poles. Together with the pressure-gradient force it produces the geostrophic wind and the rotation of cyclones.

State PCS 2023 Q144 — Geography PYQ with Answer

State PCS 2023 Q144 — Geography PYQ with Answer