Question

question 12 (1 point)
if the velocity versus time graph of an object is a horizontal line, the object is
○ moving with constant non - zero speed.
○ moving with constant non - zero acceleration.
○ at rest.
○ moving with infinite speed.

Explanation:

1. Recall the meaning of a velocity - time graph: The velocity - time graph's slope represents acceleration ($a=\frac{\Delta v}{\Delta t}$), and the y - axis (ordinate) represents velocity.
2. Analyze a horizontal line on a velocity - time graph: A horizontal line means that the velocity ($v$) does not change with time ($\Delta v = 0$).

• For the option "moving with constant non - zero acceleration": Acceleration $a=\frac{\Delta v}{\Delta t}$. If $v$ is constant, $\Delta v = 0$, so $a = 0$, not constant non - zero acceleration. Eliminate this option.
• For the option "at rest": If the object is at rest, the velocity should be zero. A horizontal line can have a non - zero velocity (e.g., a horizontal line at $v = 5\ m/s$). So this option is incorrect.
• For the option "moving with infinite speed": A horizontal line on a velocity - time graph represents a constant finite velocity (since the graph has a finite value on the velocity axis), not infinite speed. Eliminate this option.
• For the option "moving with constant non - zero speed": Since velocity is speed with direction, a constant velocity (horizontal line on $v - t$ graph) means constant speed (and constant direction). If the velocity is non - zero (the horizontal line is not on $v = 0$), then the object is moving with constant non - zero speed.

Answer:

A. moving with constant non - zero speed.