Equilibrium of Forces

Contents / notes

• Equilibrium of particles.
• Equilibrium of coplanar forces.
• Triangles and polygon of forces.
• Lami's theorem.
• Principles of moments.
• Moment of a force.
• Simple treatment and moment of a couple (torque).
• Applications of moments.
• Conditions for equilibrium of rigid bodies under parallel and non-parallel forces.
• Resolution and composition of forces in two perpendicular directions.
• Resultant and equilibrant.
• Centre of gravity and stability.
• Stable, unstable and neutral equilibrium.

Candidate objectives

• Apply the conditions for equilibrium of coplanar forces to solve problems.
• Use the triangle and polygon laws of forces to solve equilibrium problems.
• Use Lami's theorem to solve problems.
• Analyse the principle of moments of a force.
• Determine the moment of a force and a couple.
• Describe applications of moments of a force and a couple.
• Apply the conditions for equilibrium of rigid bodies to solve problems.
• Resolve forces into two perpendicular directions.
• Determine the resultant and equilibrant of forces.
• Differentiate between stable, unstable and neutral equilibrium.