Here's why:

* Mechanical waves transfer energy through the vibrations or oscillations of particles within the medium. Think of a ripple in a pond. The water molecules move up and down, transferring energy from one to the next.

* Without a medium, there's nothing to vibrate, so the wave cannot travel. Sound waves, for example, need air, water, or solids to travel. In a vacuum, sound cannot exist.

Examples of Mechanical Waves:

* Sound waves: Travel through air, water, and solids.

* Water waves: Travel on the surface of water.

* Seismic waves: Travel through the Earth's crust.

Let me know if you'd like to delve into the different types of mechanical waves!