What effect does friction have on the total mechanical energy of a pendulum in motion?

Friction acts as a dissipative force in a pendulum’s motion, which means it transforms some of the mechanical energy into other forms of energy, primarily thermal energy. As the pendulum swings back and forth, friction acts at various points—most notably at the pivot point and along the path of the swing. This resistance gradually reduces the amplitude of the swing, leading to a decrease in the maximum height attained by the pendulum.

In an ideal system without friction, mechanical energy is conserved; potential energy converts to kinetic energy and vice versa without any loss. However, the presence of friction means that not all the initial mechanical energy remains in the system as the pendulum moves. Each swing loses some energy due to friction, resulting in a decline in the total mechanical energy available to the system over time.

In summary, friction decreases the mechanical energy of the pendulum as it results in energy loss through conversion to heat, which ultimately leads to the gradual stopping of the pendulum’s motion.