* Acceleration measures change in velocity. If an object is moving at a constant speed in a straight line, its velocity is not changing, meaning its acceleration is zero.
* Motion is simply a change in position. Even though the object isn't speeding up or slowing down, it's still moving.
Examples:
* A car traveling at a steady 60 mph on a straight highway: It has zero acceleration because its velocity is constant, but it's definitely in motion.
* A ball rolling across a frictionless surface: Once the initial force that set it in motion is gone, the ball continues at a constant velocity with zero acceleration.
Key takeaway: Zero acceleration means the object's velocity is not changing. It doesn't mean the object is at rest.
