Final answer:
The equilibrium position of a pendulum is when it is hanging straight down, with the angle of displacement being zero. This position represents a state of balanced forces where the pendulum, if undisturbed, would remain at rest.
Step-by-step explanation:
When a pendulum hangs straight down, it is at its equilibrium position. This is the point where the forces acting on the pendulum are balanced, and if undisturbed, the pendulum would remain stationary. The correct statement about the equilibrium position of a pendulum is option b, which suggests that the pendulum is hanging straight down. This position is characterized by the angle of displacement being zero. It is not when the tension in the string is zero, nor when it is maximum, and it is unrelated to the weight variance of the pendulum bob.
Everyday examples of pendulums, including clocks and swings, illustrate objects that undergo simple harmonic motion when displaced by a small angle. This behavior is reflected in a simple pendulum, which consists of a small mass (the pendulum bob) suspended by a light string or wire. The return to the equilibrium position demonstrates the restorative force acting on the pendulum, which is directly proportional to its displacement when the angle is small.