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AP Calculus BC 1.9 Connecting Multiple Representations of Limits Exam Style Questions – FRQ

AP Calculus BC 1.9 Connecting Multiple Representations of Limits Exam Style Questions - FRQ

Question (Hard)

A particle moves along the \( x \)-axis with acceleration \( a(t) = 12t^2 – 4 \) ft/sec² for \( t \geq 0 \). Initial velocity \( v(0) = 0 \), position \( x(1) = 3 \) feet.

(a) Find velocity \( v(t) \).
(b) Use the table to estimate \( \lim_{t \to 1} v(t) \). Explain if it matches \( v(1) \) from (a).
(c) Find position \( x(t) \).

\( t \) (sec)0.90.990.9991.0011.011.1
\( v(t) \) (ft/sec)-1.956-1.9996-1.999996-2.000004-2.0004-2.044
▶️ Answer/Explanation

Solution

(a) \( v(t) = \int (12t^2 – 4) \, dt = 4t^3 – 4t + C \). Using \( v(0) = 0 \), \( C = 0 \). \( \boxed{v(t) = 4t^3 – 4t} \).

(b) From table, as \( t \to 1^- \): \( v(0.999) = -1.999996 \to -2 \). As \( t \to 1^+ \): \( v(1.001) = -2.000004 \to -2 \). \( \boxed{\lim_{t \to 1} v(t) = -2} \). Compute \( v(1) = 4(1)^3 – 4(1) = 0 \), which differs from -2, indicating a removable discontinuity.

(c) \( x(t) = \int (4t^3 – 4t) \, dt = t^4 – 2t^2 + C \). With \( x(1) = 3 \), \( 1 – 2 + C = 3 \implies C = 4 \). \( \boxed{x(t) = t^4 – 2t^2 + 4} \).

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