Go to urbandictionary.com, and search 69er. Then you will get your anser.
Constant speed has no acceleration, whereas changing speed does.
A meaningless arrangement of words.
Yes; acceleration is any change in velocity - speed, or direction.
It is not necessarily a motion in itself... Variable speed refers to something that can change speeds, or that the speeds can be changed. There are many things that can be variable speed.
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