A balloon is tied to a ground point by a cable that can extend and retract

MATHEMATICS · Subjective · AP · Calculus AB · Contextual Applications of Differentiation · Contextual Applications of Differentiation

Problem

A balloon is tied to a ground point by a cable that can extend and retract. At a particular instant the balloon is 42\,m horizontally from the tie-down point and 42\,m above it, so the cable makes an angle θ=π4\theta = \dfrac{\pi}{4} with the ground. At that instant the balloon’s horizontal velocity is 4.0\,m\!/s away from the tie-down point and its vertical velocity is 2.0\,m\!/s upward. Compute dθdt\dfrac{d\theta}{dt} at that moment, expressing your answer in rad/s and indicating its sign.

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