If a pendulum is not pushed, why does it not go as big when it swings back. Where does the lost PE go?

ans. Since there is no force applied to the pendulum there is not enough Kinetic energy (energy of motion) to transform into potential energy to make it swing back. The pendulum will not swing back as high due to gravity which will push the pendulum down. The lost PE is stored in the pendulum and makes it stationary until it is pushed.

The reason a pendulum does not swing back as high when it is not pushed is because there is no external force acting on it to increase its potential energy (PE). In a pendulum, the potential energy is converted into kinetic energy (KE) as it swings back and forth.

When a pendulum is at its highest point (the maximum potential energy), there is no external force acting on it, so it does not have enough energy to swing back to the same height on the other side. As the pendulum swings down, gravity acts on it, converting the potential energy to kinetic energy. At the lowest point of the swing, the pendulum has the maximum kinetic energy and minimal potential energy.

However, due to factors like air resistance and friction, some of the energy is lost in the form of heat and sound. This loss of energy reduces the total mechanical energy of the pendulum. Thus, when the pendulum swings back, it cannot reach the same maximum height as before because it has less total energy to convert into potential energy.

The lost potential energy is not completely lost, but rather stored within the system of the pendulum. This stored energy helps maintain the pendulum in a stationary position until it is pushed or disturbed again, at which point it can convert the stored energy back into kinetic energy and further swinging motion.

In summary, when a pendulum is not pushed, it does not have enough energy to swing back to the same height due to the absence of an external force. The lost potential energy is stored within the pendulum, keeping it stationary until another force is applied.