Difficulty: Medium

Average Score: 68%

A runner jogs and slows to a stop after crossing the finish line. How are speed and velocity affected?

Rationale

Both velocity and speed change.

As the runner slows to a stop after crossing the finish line, both their speed and velocity decrease. Speed, which is a scalar quantity representing how fast an object is moving, diminishes as the runner decelerates, while velocity, being a vector quantity that includes direction, also changes since the runner transitions from a positive speed to zero.

A (Velocity changes, but speed does not.) YOUR ANSWER

This statement is incorrect because while it is true that velocity changes as the runner comes to a stop, speed also decreases from a positive value to zero. Speed is inherently affected by the runner's deceleration, making this option misleading.

B (Both velocity and speed change.) CORRECT

This is the correct answer since both speed and velocity decrease as the runner slows down to a complete stop. Speed diminishes from its initial value, and velocity changes from a positive value to zero, reflecting the change in motion.

C (Neither speed nor velocity changes.) YOUR ANSWER

This option is incorrect because it overlooks the fact that as the runner slows down, both speed and velocity are indeed changing. The runner's motion is characterized by a reduction in both quantities as they come to a stop.

D (Speed changes, but velocity does not.) YOUR ANSWER

This choice is incorrect because, although speed does change as the runner decelerates, velocity also changes due to the runner's change in motion from moving to a complete stop. Ignoring the change in velocity misrepresents the nature of the runner's motion.

Conclusion

In summary, as the runner slows to a stop after crossing the finish line, both speed and velocity are affected. Speed decreases as the runner decelerates, and velocity transitions from a positive value to zero, reflecting the cessation of motion. Understanding this distinction is crucial in differentiating between scalar and vector quantities in physics.

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