Inhabitants are unaware of the speed of rotation of the planet Earth because 1. the angular velocity is constant for each place on the Earth’s surface 2. the atmosphere rotates with the Earth 3. there are no nearby objects, either stationary or moving at a rate different from that of the Earth Which of the above is/are the correct explanation(s)?
- (a)1 only
- (b)1 and 2 only
- (c)2 and 3 only
- (d)1, 2 and 3
Correct — D, 1, 2 and 3. We do not sense the Earth spinning because all three explanations hold together. The rotation is at a constant angular velocity (1), so there is no changing speed and no jolt to feel — we only feel changes in motion (acceleration), not steady motion. The atmosphere and everything on the surface rotate along with the Earth (2), so the air does not rush past us. And there is no nearby fixed or differently-moving object to compare against (3), so there is no visible reference to reveal the motion. All three are correct explanations.
- (a)1 only — Constant angular velocity is one reason, but it alone does not explain why the air is still around us or why we see no relative motion — statements 2 and 3 are also valid.
- (b)1 and 2 only — True as far as it goes, but it omits statement 3 — the absence of a nearby differently-moving reference object, which is also a correct explanation.
- (c)2 and 3 only — It wrongly drops statement 1; the constancy of the angular velocity (no acceleration to feel) is a genuine part of the explanation.
Steady, unchanging motion produces no sensation — our bodies detect acceleration (a change in speed or direction), not constant velocity. The Earth rotates once a day at an almost constant angular velocity, carrying its atmosphere and everything on it along uniformly, so there is nothing to feel and, without an outside reference, nothing to see.
The idea mirrors sitting in a smoothly cruising train or aircraft: at constant speed with the cabin air moving with you and no view of the ground, you cannot tell you are moving. The Earth is the same situation on a planetary scale, so all three statements combine into the answer.
- The Earth completes one rotation in about 24 hours, spinning west to east.
- Humans sense acceleration, not uniform (constant-velocity) motion.
- The atmosphere co-rotates with the Earth, so there is no perpetual wind from the spin.
- Without a nearby stationary or differently-moving reference, the rotation is not visually obvious from the surface.
- Assuming only the 'constant angular velocity' reason matters and skipping the atmosphere and reference-object points.
- Confusing being unaware of steady rotation with the real effects rotation does produce (day/night, Coriolis deflection).
As a multi-statement 'which explanation(s)' item testing the reasoning behind not feeling the Earth's spin.
No directly related past PYQ was found.
- practice — not a real PYQ
A passenger in a train moving at a constant high speed on a straight, smooth track does not feel the motion mainly because
- (a)the train has no engine noise
- (b)the body senses acceleration, not constant velocity
- (c)the train is lighter than the passenger
- (d)gravity cancels the motion
Answer(b) the body senses acceleration, not constant velocity — the same reason we do not feel the Earth's steady rotation.
- practice — not a real PYQ
The apparent deflection of winds and ocean currents caused by the Earth's rotation is called the
- (a)Coriolis effect
- (b)Doppler effect
- (c)Greenhouse effect
- (d)Tyndall effect
Answer(a) Coriolis effect — a real consequence of the rotation we otherwise cannot feel.