do electromagnetic waves travel slower than mechanical waves?

No, electromagnetic waves travel faster than mechanical waves. In a vacuum, electromagnetic waves, such as light, travel at a constant speed of about 299,792 kilometers per second (186,282 miles per second), which is the fastest speed possible in the universe. Mechanical waves, on the other hand, require a medium (such as air, water, or solid material) to propagate and they travel at much slower speeds.