Which of the following best describes the velocity-time graph for an object moving with uniform velocity?
A straight horizontal line parallel to the time axis
A velocity–time (v–t) graph plots velocity on the y-axis against time on the x-axis. Two features of such a graph carry physical meaning: the slope of the line equals the object's acceleration, and the area between the line and the time axis equals the displacement covered.
Reasoning for uniform velocity:
Why the other shapes are wrong: A straight line sloping upward from the time axis represents uniformly increasing velocity, i.e. constant (uniform) acceleration, not constant velocity. A line starting from the origin and sloping upward is the special case of an object accelerating uniformly from rest — again not uniform velocity. A curved line above the time axis means the slope itself is changing, so the acceleration is non-uniform. Only the horizontal line gives zero acceleration and therefore truly uniform velocity.
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