iGCSE Physics (0625) 1.5.3 Conditions for equilibrium -Exam Style Questions Paper 1- New Syllabus
▶️ Answer/Explanation
Detailed solution:
An object is more stable when its centre of mass is positioned as low as possible, which increases the angle through which it can be tilted before toppling.
For the lamp, a low centre of mass means the weight acts through the base even if it is nudged, preventing it from falling over easily.
Options B, C, and D describe features that would actually make the lamp less stable (e.g., top-heavy or narrow base).
Therefore, the correct requirement for stability is a low centre of mass.
▶️ Answer/Explanation
Detailed solution:
When an object is freely suspended from a pivot point, the only forces acting on it are its weight and the upward reaction force at the pivot.
The weight of the object acts through its centre of gravity. If the centre of gravity is not directly below the pivot, the weight creates a moment (turning effect) that causes the object to swing.
Equilibrium is reached only when there is no resultant moment, which happens when the line of action of the weight passes directly through the pivot $O$.
Therefore, once the object comes to rest, the centre of gravity must be located on the vertical line passing through the point of suspension.
Specifically, for stable equilibrium in a hanging object, the centre of gravity lies vertically below the pivot $O$.
This matches Option D.
▶️ Answer/Explanation
Detailed solution:
Stability depends on the position of the centre of gravity ($CG$) and the width of the base.
An object is least stable if its $CG$ is high and its base is narrow.
The letter ‘T’ has a heavy top section and a very narrow base point supporting it.
This results in a high $CG$ relative to its contact area with the table.
When knocked, the line of action of its weight easily falls outside the narrow base.
Thus, letter ‘T’ is the most likely to topple compared to ‘A’, ‘M’, or ‘X’.