UPSC Prelims 2003 · General Studies

Question 37: Science and Technology

An oil tanker is partially filled with oil and moves forward on a level road with uniform acceleration. The free surface of oil then

aRemains horizontal

bIs inclined to the horizontal with smaller depth at the rear end

cIs inclined to the horizontal with larger depth at the rear end

dAssumes parabolic curve

AnswerThe answer is (c).

When the tanker accelerates forward, the oil, by inertia, lags behind and piles up towards the rear. The free surface settles at an angle to the horizontal with tan(theta) = a/g, so the oil is deeper at the rear and shallower at the front. The surface stays a plane (a straight line in section), not a parabola; a parabolic surface arises in a rotating container. If the tanker braked, the oil would pile up at the front instead.

Why each option is right or wrong

(a) The surface is horizontal only when there is no acceleration.
(b) With forward acceleration the depth is smaller at the front, not at the rear.
(c) Correct: inclined, with larger depth at the rear.
(d) A parabolic surface occurs in a rotating container, not under straight-line acceleration.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2003, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.