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Ch 09: Rotation of Rigid Bodies
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Non è quello che usi tu?Cambia libro di testo
Capitolo 9, Problema 3b

The angular velocity of a flywheel obeys the equation ωz(t) = A + Bt2, where t is in seconds and A and B are constants having numerical values 2.75 (for A) and 1.50 (for B). What is the angular acceleration of the wheel at (i) t = 0 and (ii) t = 5.00 s?

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Understand the problem: The angular velocity of the flywheel is given as a function of time, \( \omega_z(t) = A + B t^2 \), where \( A = 2.75 \) and \( B = 1.50 \). Angular acceleration is the time derivative of angular velocity, \( \alpha(t) = \frac{d\omega_z(t)}{dt} \). We need to calculate \( \alpha(t) \) at \( t = 0 \) and \( t = 5.00 \ \text{s} \).
Differentiate the angular velocity equation with respect to time to find the angular acceleration: \( \alpha(t) = \frac{d}{dt}(A + B t^2) \). Since \( A \) is a constant, its derivative is zero, and the derivative of \( B t^2 \) is \( 2 B t \). Thus, \( \alpha(t) = 2 B t \).
Substitute the value of \( B = 1.50 \) into the angular acceleration equation: \( \alpha(t) = 2 (1.50) t = 3.00 t \). This is the expression for angular acceleration as a function of time.
To find the angular acceleration at \( t = 0 \), substitute \( t = 0 \) into \( \alpha(t) = 3.00 t \): \( \alpha(0) = 3.00 (0) \). Simplify to find the angular acceleration at \( t = 0 \).
To find the angular acceleration at \( t = 5.00 \ \text{s} \), substitute \( t = 5.00 \) into \( \alpha(t) = 3.00 t \): \( \alpha(5.00) = 3.00 (5.00) \). Simplify to find the angular acceleration at \( t = 5.00 \ \text{s} \).

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