If an object is NOT accelerating, then one knows for sure that it is ___.

A. at rest

B. moving with a constant speed

C. slowing down

D. maintaining a constant velocity

"Zero acceleration" means "velocity" that's not changing.

Sadly, it seems that both of these words are almost always

misinterpreted and misunderstood. "Acceleration" does NOT

mean "speeding up", and "velocity" does NOT mean speed.

"Velocity" is the speed AND direction of motion. So, for example,

'30 miles per hour north' and '30 miles per hour west' are the same

speed but different velocities.

"Acceleration" is ANY change in speed OR direction. Consider three

different families in three different cars. One car is speeding up, one is

slowing down, and the third is driving around a curve at a steady speed.

ALL three of the cars are accelerating.