A ball is observed after being projected vertically upward

PHYSICS · Single correct · AP · Physics C: Mechanics · Kinematics · Kinematics

Problem

A ball is observed 3 s3\,\text{s} after being projected vertically upward. Its speed at that instant is 5 m s−15\,\text{m}\,\text{s}^{-1} downward. The observer now decides to redefine the downward direction as positive for all subsequent measurements. What value should be recorded for the ball’s velocity immediately after this change of axis? (a) −5 m s−1-5\,\text{m}\,\text{s}^{-1} (b) +10 m s−1+10\,\text{m}\,\text{s}^{-1} (c) +5 m s−1+5\,\text{m}\,\text{s}^{-1} (d) 0 m s−10\,\text{m}\,\text{s}^{-1}

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