Final answer:
The motion of a pendulum is predominantly affected by gravity, creating a restoring force, and the tension in the string, which guides the pendulum's arc-like oscillation. The period of a pendulum is dependent on its length and the acceleration due to gravity, not the mass of the bob.
Step-by-step explanation:
Forces Affecting a Pendulum's Motion
In addition to gravity, the other predominant force affecting the motion of a pendulum is the restoring force arising from the tension in the string. This force is crucial for the oscillation of the pendulum. When a pendulum swings, gravity acts to pull it back towards the equilibrium position, creating a restoring force that is a component of the gravitational force. As the pendulum moves, the tension in the string exerts a force perpendicular to the direction of gravity, which along with the component of gravity, causes the pendulum to follow an arc-like path.
The motion of a pendulum is not affected by the mass of the bob; instead, it is the length of the pendulum and the acceleration due to gravity that determines its period. For a simple pendulum, the period formula shows that the period (T) is independent of the mass and is given by T = 2π√(L/g), where L is the length and g is the acceleration due to gravity.
Thus, the primary forces that cause a pendulum to oscillate are gravity, providing the restoring force, and the tension in the string, allowing for the pendulum's arc path during its swing.