Which scenario is NOT an example of acceleration?

• A. A car going around a curve in the road at a constant speed
• B. A car driving in a straight line that changes speed from 20 mph to 40 mph
• C. A car going around a curve that changes speed from 20 mph to 40 mph
• D. A car driving in a straight line at a constant speed

Answer: (D)

Acceleration is a change in velocity over time. Velocity includes both speed and direction, so any change in either means there is acceleration.

A car going around a curve at constant speed changes direction, so its velocity changes and it experiences acceleration (centripetal). A car in a straight line that speeds up from 20 mph to 40 mph changes its speed, so there is acceleration. A car going around a curve that also changes speed from 20 mph to 40 mph changes both speed and direction, so it definitely accelerates. A car driving straight at a constant speed keeps both its speed and direction the same, so its velocity doesn’t change and there is no acceleration.

Therefore, the scenario that is not an example of acceleration is the straight-line motion at a constant speed.