Accelerated Motion on a Circular Path

Accelerated motion occurs when there is a change in velocity over time. Velocity is a vector quantity, meaning it has both magnitude (speed) and direction.

In this scenario:

• The athlete runs at a constant speed. This means the magnitude of the velocity is unchanging.
• The athlete runs along a circular path. In circular motion, the direction of motion is continuously changing.

Because the direction of motion is constantly changing, the athlete's velocity is changing, even though the speed is constant. A change in velocity signifies acceleration.

Analysis of Options

• Option 1: The mass of the athlete is constant - Mass does not directly determine if motion is accelerated.
• Option 2: The athlete's speed is increasing - This contradicts the problem statement, which specifies constant speed.
• Option 3: A constant external force is applied - While a centripetal force is required for circular motion (causing acceleration), the fundamental reason the motion *is* accelerated is the resulting change in velocity, not merely the presence of the force itself.
• Option 4: The direction of motion changes continuously - This directly explains why the velocity changes, leading to acceleration.

Therefore, the motion is accelerated because the direction of motion changes continuously.