Assertion (A): The weight of a body decreases with the increase of latitude on earth. Reason (R): The earth is not a perfect sphere.

Answer: (d) A is false but R is true

Weight rises towards the poles, so A is false; the Earth is an oblate spheroid, so R is true.

The idea

Weight is mass multiplied by local effective gravity. Towards the poles, Earth’s smaller radius brings the surface closer to the centre, and the outward effect associated with rotation decreases. Both effects make a body’s weight generally greater at higher latitudes.

Move from equator towards a pole → Surface lies closer to Earth’s centre → Gravitational pull becomes stronger → Outward rotational effect decreases → Effective gravity increases → The same mass weighs more

Why the others are wrong

(a) A is false.

(b) A is false — weight increases with latitude.

(c) A is false.

The trap

Statement A reverses the direction.

Elimination technique

The asserted decrease in weight reverses the physical trend, so A is false. Only (d) allows a false A; the reason is independently true because Earth is not a perfect sphere.

Also know

Mass does not change when a body moves between latitudes. Weight also falls with increasing altitude in the simple model because distance from Earth’s centre increases. Earth’s equatorial bulge and polar flattening form an oblate spheroid; local rock density and terrain cause smaller additional variations.