I shot an arrow, into the air. The acceleration is constant, due to gravity alone, at -32 k . There is no air resistance in this story.
Time is in seconds, and all distances are in feet.
We can use that to think about orbits of planets, or satellites around the Earth. This idea is explored in more depth in the next lecture, where Kepler's laws are developed. Those are separated out into the tangential and the normal components of the acceleration. Remember that v is the speed.