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Choosing which direction counts as positive in a projectile problem affects:
AThe flight time itself
BThe value of g itself
CThe signs of components
DThe physical outcome
Answer & Solution
Correct answer: C. The signs of components
1. A coordinate system is a description rather than a physical fact.
2. If you arrange the coordinate system such that the downwards direction is positive, then acceleration due to gravity takes a positive value.
3. The same fall would carry a negative sign under the opposite convention.
4. Where the ball lands and how long it takes do not depend on that choice.
5. The magnitude of g is a property of the Earth rather than of the axes.
_Source: OpenStax College Physics for AP(R) Courses 2e (CC BY 4.0), Ch 3 'Two-Dimensional Kinematics', sections 3.1-3.4_
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