How can the rotational direction of a body acted on by a single force be reversed without changing the force magnitude?
ABy doubling the mass of the body
BBy applying the same force for longer time
CBy increasing the distance from the pivot
DBy shifting the force across the pivot point
Answer & Solution
Correct answer: D. By shifting the force across the pivot point
1. Direction of rotation depends on whether the moment is clockwise or anticlockwise.
2. Shifting the point of application of the force across the pivot flips the sign of its moment.
3. So a clockwise turn becomes an anticlockwise turn.
4. Changing mass, magnitude or duration of force does not by itself flip rotation direction.
5. Hence option B is correct.
_Source: Selina Concise Physics ICSE Class 10, Ch 1 'Force' (icsehelp.com chapter extract)_
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