Final answer:
Mark, running in a circle at 10 m/s, is experiencing centripetal acceleration, which occurs due to the continuous change in the direction of velocity in circular motion.
Step-by-step explanation:
Mark is running in a circle at a speed of 10 m/s. He is indeed accelerating because acceleration is defined as a change in velocity, which includes changes in direction, not just speed. As Mark runs in a circle, the direction of his velocity is constantly changing, even if his speed is constant, leading to what is known as centripetal acceleration. This type of acceleration is always directed toward the center of the circular path.
Centripetal acceleration can be calculated using the formula a = v^2/r, where 'v' is the linear speed and 'r' is the radius of the circular path. This equation highlights the fact that even if the speed ('v') remains constant, the mere act of following a curved path necessitates an inward (centripetally directed) acceleration.