Question

According to principal of moments, a body will be in rotational equilibrium if-
1. algebraic sum of the moments of all forces acting on the body, about a fixed point is infinity
2. algebraic sum of the moments of all forces acting on the body, about a fixed point is a non zero finite quantity
3. algebraic sum of the moments of all forces acting on the body, about a fixed point is zero
4. none of the above

Answer 1

Correct Answer - Option 3 : algebraic sum of the moments of all forces acting on the body, about a fixed point is zero

CONCEPT:

• Principle of moments: A body will be in rotational equilibrium if the algebraic sum of the moments of all forces acting on the body, about a fixed point is zero.
• Moment of force: It is also called torque.
  • The torque due to a force gives us the turning effect of the force about the fixed points on the axis.
  • It is measured as the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis of rotation

EXPLANATION:

• Rotational equilibrium: According to the principle of moments, a body will be in rotational equilibrium if the algebraic sum of the moments of all forces acting on the body, about a fixed point is zero.
• Hence option 3) is correct.