Here's why:

* Pulse as a Wave: A pulse is a wave that travels through a medium, like a string or the air. Waves are disturbances that transfer energy through a medium without transferring matter.

* Mechanical Waves: Mechanical waves require a medium to travel. They involve the vibration or oscillation of particles in the medium. Examples include sound waves, water waves, and seismic waves.

* Electromagnetic Waves: Electromagnetic waves do not require a medium to travel. They are disturbances in electric and magnetic fields that propagate through space. Examples include light, radio waves, and X-rays.

Therefore, since a pulse needs a medium to travel, it is classified as a mechanical wave.