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What must always be present to cause a centripetal acceleration, according to Newton's second law of motion?
AA net external force
BA constant angular velocity
CA frictionless surface
DA fixed radius of curvature
Answer & Solution
Correct answer: A. A net external force
1. Newton's second law states that a net external force is required to produce any acceleration.
2. Centripetal acceleration is still an acceleration, so it too requires a net external force to exist.
3. A constant angular velocity or a fixed radius describes the motion's geometry, not the cause of the acceleration, and a frictionless surface is not required at all, since many other forces can supply the needed force.
4. Only a net external force satisfies Newton's second law as the cause of the centripetal acceleration.
_Source: OpenStax College Physics (CC BY 4.0), Ch 6 "Uniform Circular Motion and Gravitation", section 6.2 Centripetal Acceleration_
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