Acceleration-time graphs show how an object's acceleration changes over time. The area under the graph represents the change in velocity. Here are four common types of acceleration:
A horizontal line at zero acceleration indicates either constant velocity (object moving at steady speed) or the object is at rest (not moving at all). In both cases, there is no change in velocity over time.
A horizontal line above the time axis shows constant positive acceleration. The object's velocity increases at a steady rate in the positive direction.
A horizontal line below the time axis indicates constant negative acceleration (deceleration). The object's velocity decreases at a steady rate.
A curved line shows changing acceleration. The slope of the acceleration-time graph represents the rate of change of acceleration (jerk).