It covers equal distances in equal intervals of time.
Explanation
Uniform motion along a straight line (rectilinear motion) is defined as motion where an object travels with a constant velocity. This implies that the object maintains a constant speed and moves in a fixed direction without any acceleration.
Option Analysis
- It covers equal distances in equal intervals of time. is Correct: By definition, an object is in uniform motion if it covers equal distances in equal intervals of time, however small these time intervals may be. This indicates a constant speed along the straight path.
- It moves along a circular path with constant speed. is Incorrect: Motion along a circular path involves a continuous change in direction at every point. Even if the speed is constant, the change in direction results in a change in velocity. Therefore, uniform circular motion is an example of accelerated motion, not uniform motion in the context of velocity.
- It covers unequal distances in equal intervals of time. is Incorrect: If an object covers unequal distances in equal intervals of time, its speed is changing. This characterizes non-uniform or accelerated motion.
- It possesses a constantly changing velocity. is Incorrect: Velocity is a vector quantity comprising both speed and direction. If velocity is constantly changing (either due to speed or direction), the motion is accelerated, which contradicts the definition of uniform motion.
Key Takeaway: Uniform motion along a straight line strictly requires zero acceleration, meaning the object must cover equal distances in equal time intervals.