From the definition of average velocity,
,
and the fact that constant acceleration means
we can solve for the time 
:
Answer:
15? I actually don't know
A mechanical wave<span> is a </span>wave<span> that is an oscillation of </span>matter<span>, and therefore transfers energy through a </span>medium.[1]<span> While waves can move over long distances, the movement of the </span>medium of transmission<span>—the material—is limited. Therefore, oscillating material does not move far from its initial equilibrium position. Mechanical waves transport energy. This energy propagates in the same direction as the wave. Any kind of wave (mechanical or electromagnetic) has a certain energy. Mechanical waves can be produced only in media which possess elasticity and inertia.</span>
