Q. The weight of an object at the poles is greater than at the equator. This is because (UPSC Prelims/1979)
Correct Answer: (a) Of the shape of the earth
Why option (a) is correct?
• Earth is an oblate spheroid (flattened at poles, bulged at equator)
• Radius of Earth is smaller at poles than at equator
• Gravitational acceleration (g) is inversely proportional to square of radius
• Smaller radius at poles → greater value of g → greater weight
• Earth is an oblate spheroid (flattened at poles, bulged at equator)
• Radius of Earth is smaller at poles than at equator
• Gravitational acceleration (g) is inversely proportional to square of radius
• Smaller radius at poles → greater value of g → greater weight
Role of Earth’s Rotation
• Centrifugal force is maximum at the equator
• Centrifugal force is zero at the poles
• Centrifugal force reduces effective gravity at equator
Why other options are incorrect?
• Moon’s attraction is negligible compared to Earth’s gravity
• Sun’s attraction does not cause daily weight variation
• Gravitational pull being more at poles is an effect, not the root cause
Key Formula
• Weight (W) = m × g
• Mass remains constant; g varies with location
Comparison: Poles vs Equator
• Poles → Minimum radius, zero centrifugal force, maximum weight
• Equator → Maximum radius, maximum centrifugal force, minimum weight