What does a horizontal line on a velocity–time graph indicate about the object's motion?

What does a horizontal line on a velocity–time graph indicate about the object's motion?

• A. The object is at rest
• B. The velocity is constant
• C. Acceleration is increasing
• D. Displacement is decreasing

Answer: (B)

A horizontal line on a velocity–time graph means the velocity doesn’t change as time passes. The slope of the line is zero, so the acceleration is zero. With zero acceleration, the velocity remains constant, which can be zero (the object is at rest) or some nonzero value (the object moves at a steady speed in one direction). It doesn’t imply acceleration is increasing. Displacement behavior isn’t fixed by this alone: if the constant velocity is positive, displacement increases linearly; if negative, displacement decreases. The key idea is that a flat line shows constant velocity (and zero acceleration).

A horizontal line on a velocity–time graph means the velocity doesn’t change as time passes. The slope of the line is zero, so the acceleration is zero. With zero acceleration, the velocity remains constant, which can be zero (the object is at rest) or some nonzero value (the object moves at a steady speed in one direction). It doesn’t imply acceleration is increasing. Displacement behavior isn’t fixed by this alone: if the constant velocity is positive, displacement increases linearly; if negative, displacement decreases. The key idea is that a flat line shows constant velocity (and zero acceleration).