A block of mass m, attached to a spring, oscillates horizontally on a surface. The coefficient of friction between the block and the surface is µ. Which of the following trajectories best describes the motion of the block in the phase space (xp_x-plane)?

Concept:

Coefficient of friction (COF) is a dimensionless number that is defined as the ratio between friction force and normal force. The presence of this implies friction.

Calculation:

The presence of friction makes the amplitude and momentum of oscillation continuously decreases.

The correct answer is option (2).