Answer:
it's possible to calculate an object's velocity at any moment along its path. This is called instantaneous velocity and it is defined by the equation v = (ds)/(dt),in other words, the derivative of the object's average velocity equation.
Explanation:
If a body does not cover a equal distance at a equal interval of time it is said to be non uniform motion...

Not sure.can you give me a clue?
Answer:
D.
Explanation:
Given that your boat departs from the bank of a river that has a swift current parallel to its banks. If you want to cross this river in the shortest amount of time, you should direct your boat: so that it drifts with the current.
If the boat moves perpendicular to the current, the current flow will be the resistance to the movement of the boat. So, it's better for the boat to drifts perpendicularly with the current.
The best answer is therefore option D.
The Doppler effect occurs when a source of sound or light
moves either toward or away from the observer.