Question

The diagram in Fig. shows the displacement- time graph of a vibrating body. Why is the amplitude of vibrations gradually decreasing ?

Answer 1

The simple harmonic oscillations at constant amplitude, oscillating are shown in Figure between $-aand+a$. Harmonic oscillations tend to die away as time goes on. This behavior, called damping of the oscillations, is produced by forces such as friction and viscosity. These forces are known collectively as dissipative forces because they tend to dissipate the potential and kinetic energies of macroscopic bodies into the energy of the chaotic motion of atoms and molecules known as heat.
If the total mechanical energy of an oscillating body were conserved, the system would oscillate indefinitely with the same amplitude. In any real situation, however, there are always non-conservative forces such as friction or drag forces present. These dissipative forces decrease the system's total mechanical energy and can be either internal or external to the system. The amplitude will gradually decrease and the oscillations will die out.