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AP® Physics C: Mechanics

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Difficult

Kinematics Polynomials: Object Direction Change

APPHMC-1MRKYN

A toy car moves in one dimension, with a velocity described by the function $v(t)=-{t}^{2}+4t+5$, during the interval $0{ }\le { }t\le { }7$. The velocity, $v(t)$, is measured in m/s when $t$ is measured in seconds.

Determine when, if ever, the toy car changes direction for the first time.

A

$t=-1s$

B

$t=2s$

C

$t=5s$

D

$t=9s$

E

The object never changes direction.