Question

Mechanical waves are created when a source of energy causes a medium to ?

Answer 1

A mechanical wave is created when a source of energy causes a vibration to travel through a medium 

And yeah lol 
A mechanical wave is a disturbance in matter that carries energy from one place to another :) 

This what you needed? 

Answer 2

Mechanical waves are created when a source of energy cause a medium to "VIBRATE".