Summary
Equilibrium of forces occurs when all forces acting on an object are balanced, resulting in no net force or torque.
- Equilibrium — a state where all forces are balanced, resulting in no net force or torque. Example: A book resting on a table is in equilibrium.
- Principle of Moments — for an object to be in equilibrium, the sum of clockwise moments must equal the sum of anticlockwise moments. Example: A seesaw balanced with equal weights on both sides.
- Coplanar Forces — forces that lie in the same plane and can be represented as closed vector triangles when in equilibrium. Example: Forces acting on a stationary table.
- Common Forces — include weight, normal reaction force, tension, and friction. Example: A box on a slope experiences weight, normal force, and friction.
Exam Tips
Key Definitions to Remember
- Equilibrium: A state where all forces are balanced, resulting in no net force or torque.
- Principle of Moments: The sum of clockwise moments equals the sum of anticlockwise moments for equilibrium.
- Coplanar Forces: Forces that lie in the same plane and can form a closed vector triangle in equilibrium.
Common Confusions
- Confusing equilibrium with static objects only; objects can also move at constant velocity.
- Misunderstanding that equilibrium means no forces are acting; it means forces are balanced.
Typical Exam Questions
- What is equilibrium? Equilibrium is when all forces are balanced, resulting in no net force or torque.
- How do you determine if an object is in equilibrium using moments? Ensure the sum of clockwise moments equals the sum of anticlockwise moments.
- What are coplanar forces? Forces that lie in the same plane and can form a closed vector triangle when in equilibrium.
What Examiners Usually Test
- Understanding of the conditions for equilibrium.
- Ability to apply the principle of moments to solve problems.
- Identification of forces acting on an object in equilibrium.