occurs when waves spread out and travel around obstacles or through openings in obstacles.

diffraction

Explanation:

As you can see from the figure, sound waves spread out and travel around obstacles. This is called diffraction. It also occurs when waves pass through an opening in an obstacle.  

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be

no sign of dia of fuel cell