Question

Three parallel forces act on an object. As a result of these forces, the object is in equilibrium.

What must be correct for these forces?
A. They all act along the same line.
B. They all have the same magnitude.
C. They do not all act along the same line.
(D) They do not all have the same magnitude. (ans)

Answer 1

Three parallel forces acting on an object in equilibrium do not need to have the same magnitude or act along the same line; what is necessary is that the vector sum of all forces equals zero.

Step-by-step explanation:

For three parallel forces to hold an object in equilibrium, the following must be true:

• The forces do not necessarily have the same magnitude.
• The forces could be acting along the same line or at different points on the object.
• To achieve equilibrium, the sum of all forces and moments (torques) about any point must be zero. In other words, both the linear forces and the rotational effects must balance out.

In the case of an object with three forces acting upon it where the object remains static, it is not necessary for the forces to all act along the same line (option C). Nor do they need to have the same magnitude (option D), as the equilibrium condition is fulfilled as long as the vector sum of the forces equals zero. This means that the forces must balance, with any pulling force being countered by an equivalent pushing force in the opposite direction, or multiple forces combining to create a net force of zero.