When the pendulum bob reaches the mean position, the net force acting on it is zero. Why then does it swing past the mean position?
The motion of a pendulum can be explained by the interplay between potential energy and kinetic energy. When the pendulum bob is at the mean position, the net force acting on it is indeed zero. However, it has a certain potential energy due to its position relative to the equilibrium point.
As the pendulum bob moves away from the mean position, its potential energy is converted into kinetic energy. This causes the bob to accelerate as it swings towards the opposite side. When it reaches the opposite side, all of the potential energy has been converted into kinetic energy, resulting in maximum velocity. At this point, the kinetic energy is then converted back into potential energy, causing the bob to slow down, come to a momentary halt at the mean position, and start moving in the opposite direction.
The key point to note is that although the net force becomes zero at the mean position, the pendulum continues its motion due to the conversion between potential and kinetic energy. This phenomenon is known as mechanical energy conservation.
When a pendulum bob reaches the mean position, the net force acting on it is indeed zero. However, the motion of a pendulum is governed not only by forces but also by inertia.
When the bob reaches the mean position and momentarily comes to a stop, it possesses potential energy due to its displaced position from the equilibrium. This potential energy gets converted into kinetic energy as the bob starts moving in the opposite direction. The bob then swings past the mean position because of its inertia.
Inertia is the tendency of an object to maintain its state of motion. When the bob is at the mean position, it has zero velocity, but due to its inertia, it resists an abrupt stop. As a result, the bob overshoots the mean position and keeps swinging back and forth until energy losses, such as air resistance or friction, cause it to eventually come to a stop.
So, the swinging of a pendulum past the mean position is a result of the interplay between the potential and kinetic energy of the bob, along with the inherent property of inertia.