System of Particles and Rotational Motion

Equilibrium of a Rigid Body


  • A solid sphere, hollow sphere, disc and ring are allowed to roll down on an inclined plane simultaneously them solid sphere reaches bottom first and the ring reaches last.
  • Disc and solid cylinder reach the bottom at same time
  • Condition for equilibrium is sum of clockwise moment of forces is equal to sum of the anticlock wise moment of force.
  • Law of parallel form is sum of upwards forces is equal to two sum of downwards forces.
  • A body in equilibrium possess both translatory equilibrium and rotational equilibrium
  • When the forces are equal and does not act along the same line body will be in both translatory equilibrium but not in rotatory equilibrium.
  • When the forces are unequal and at along the same line the body will be in rotatory equilibrium but not in translatory equilibrium.
  • The forces are unequal and does not act along the same line the body will neither be in translatory equilibrium non rotatory equilibrium.
  • F1d1 = F2d2

View the Topic in this video From 0:53 To 54:20

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