Mechanics
Equilibrium of forces
Equilibrium at rest vs at constant velocityΣF = 0
Parameters
Force F₁ (right-pulling)15 N
Force F₂ (left-pulling)15 N
Mass5 kg
Calculated
Net force0.0 N
Stateequilibrium
Acceleration0.00 m/s²
Live speed0.00 m/s
Curriculum
WAECNECOIGCSESATJUPEB
📋 Teacher notes
- •Equilibrium means the resultant (net) force is zero — it does NOT mean the object is at rest. A common exam trap.
- •STATIC equilibrium: net force = 0 AND the object is at rest (stays at rest).
- •DYNAMIC equilibrium: net force = 0 but the object is already moving — it continues at constant velocity (Newton’s 1st law).
- •If the forces are unbalanced, the object accelerates — it does not matter whether it started at rest or already moving.
- •Real examples of dynamic equilibrium: a car at cruising speed (driving force = resistive forces), a skydiver at terminal velocity (weight = air resistance).
✏️ Exercises