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Multivariable Calculus

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Acceleration at Given Speed

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An object moves according to the position function:

$${\bf r}(t)=(t+3){\bf i} + t^3{\bf j} + t^3{\bf k}$$

What is the acceleration of this object when its speed is $17$?

A

$12{\bf j}+12{\bf k}$

B

${\bf i}+12{\bf j}+12{\bf k}$

C

$5{\bf i}+8{\bf j}+8{\bf k}$

D

${\bf i}+3{\bf j}+3{\bf k}$

E

$6{\bf j}+6{\bf k}$