Which condition is sufficient for a body to be in equilibrium under coplanar forces?
AThe applied forces are all equal in magnitude
BNet force is zero and net moment about any point is zero
CThe body is symmetrical about its centre of mass
DAt least one applied force passes through the pivot
Answer & Solution
Correct answer: B. Net force is zero and net moment about any point is zero
1. For equilibrium of an extended body, both translational and rotational effects must vanish.
2. The translational condition requires that the vector sum of forces equals zero.
3. The rotational condition requires that the algebraic sum of moments about any chosen point equals zero.
4. Both conditions together are necessary and sufficient.
5. The other options describe special cases that do not guarantee equilibrium on their own.
_Source: Selina Concise Physics ICSE Class 10, Ch 1 'Force' (icsehelp.com chapter extract)_
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