Since velocity is a speed and a direction, there are only two ways for you to accelerate: change your speed or change your direction—or change both. If you're not changing your speed and you're not changing your direction, then you simply cannot be accelerating—no matter how fast you're going.
Sound is a longitudinal wave.
Answer: D.) 39,200 J
Via the equation of potential energy PE = mgh where m is mass, g is the average gravity on earth and h is the height. In this case m = 400 kg, g = 9.8, h = 10 m thus:

P.E.= 39,200 Joules