The answer should be C. In this question
They both are mechanical waves.
Explanation:
Echolocation and ultrasounds are both mechanical waves that require a medium to trace through. They both process and transfer information through waves; the difference is that we humans cannot hear ultrasound waves.
Mmm tricky.
Constant velocity means there's no net force acting on the puck!
So if there's no friction or air drag force to slow it down, you don't need any force to keep that puck moving.
Once it's in motion, it stays in motion.
(Mmm isn't that a Law of Newton?)
:D