1.3.1 Forces in Equilibrium

Vectors in Equilibrium

1. When 3 vectors are in equilibrium, the resultant vector = 0.
2. After joining all the vectors tail to head, the head of the last vector will join to the tail of the first vector.

Forces in equilibrium

1. Forces are in equilibrium means the resultant force in all directions are zero.
2. When the forces acting on an object are balanced, they cancel each other out. The net force is zero.

• an object at rest is continually at rest [ velocity = 0]
• a moving object will move at constant velocity [ a = 0]

Example: The diagram above shows a load of mass 500g is hung on a string C, which is tied to 2 other strings A and B. Find the tension of string A. Answer: The tension of string C, TC = weight of the load = 5N All forces in the system are in equilibrium, hence The vertical component of tension A (T_A) = T_C T_Acos60^o = T_C T_A = T_C/cos60^o T_A = 5/cos60^o = 10N