[初賽第二階段] 力學（1） [Preliminary Phase 2] Mechanics (1)

Big Concept: Mechanics Topic: Centripetal Force Bloom's Taxonomy: Remember, Understand, Apply Learning Goal: Students can explain why an object moving in a circular motion must be continuously acted upon by an external force. Students can describe and draw the perpendicular geometric relationship between the direction of an object's velocity and the direction of its centripetal force at any given instant in circular motion. Students can distinguish the difference between "centripetal force" and ordinary pushing or pulling forces in changing the state of motion. Finally, students can identify and provide examples of "what force" provides centripetal force in everyday situations. Key Learning Points: Clearly understand that "velocity" includes magnitude (speed) and direction; a change in direction changes velocity. Know that an object will remain at rest or move in a straight line at a constant velocity when no external force acts on it (or the net force is zero). This is the absolute foundation for understanding why force is needed to turn. Understand that force is the cause of changes in an object's state of motion (causing acceleration).