Which combination of conditions correctly describes equilibrium of an extended rigid body in two dimensions?
ANet force in horizontal and vertical directions equals zero
BNet horizontal force zero, net vertical force zero, net moment zero
CSum of moments about any one chosen point equals zero
DSum of speeds and accelerations of all body points equals zero
Answer & Solution
Correct answer: B. Net horizontal force zero, net vertical force zero, net moment zero
1. A rigid body in two dimensions has three independent equilibrium conditions.
2. Vector sum of forces in the horizontal direction must be zero.
3. Vector sum of forces in the vertical direction must be zero.
4. Sum of moments about any chosen point must be zero.
5. Together these three conditions prevent both translation and rotation.
6. Option B misses rotation; option C misses translation; option D mixes unrelated kinematic terms.
_Source: Selina Concise Physics ICSE Class 10, Ch 1 'Force' (icsehelp.com chapter extract)_
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