One end of an elastic string of natural length / and modulus X is kept fixed while to the other end is attached a particle of mass m which is hanging freely under gravity. The particle is pulled down vertically through a distance x, held at rest and then released. The motion is

• A. None of these
• B. a damped oscillatory motion
• C. a rectilinear motion with constant speed
• D. a simple harmonic motion

Answer: (D)