Homework_02 - Nguyen, Thanh Homework 2 Due: Sep 7 2007,...

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Nguyen, Thanh – Homework 2 – Due: Sep 7 2007, 7:00 pm – Inst: D Weathers 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. The due time is Central time. 001 (part 1 oF 2) 10 points The velocity oF a particle moving along the x axis varies in time according to the expression v ( t ) = ( α - β t 2 ) where α = 42 . 8 m / s, β = 3 . 1 m / s 3 , and t is in seconds. ±ind the average acceleration in the time interval From t = 0 to 3 . 8 s. Correct answer: - 11 . 78 m / s 2 . Explanation: The velocities at t i = 0 and t f = 3 . 8 s are Found by substituting these values into the expression given For the velocity: v i = ( α - β t 2 i ) = (42 . 8 m / s - (3 . 1 m / s 3 ) (0 s) 2 ) = 42 . 8 m / s , v f = ( α - β t 2 f ) = (42 . 8 m / s - (3 . 1 m / s 3 ) (3 . 8 s) 2 ) = - 1 . 964 m / s . ThereFore, the average acceleration in the specifed time interval Δ t = t f - t i = 3 . 8 s is ¯ a = v f - v i t f - t i = - 1 . 964 m / s - 42 . 8 m / s 3 . 8 s - 0 s = - 11 . 78 m / s 2 . 002 (part 2 oF 2) 10 points Determine the acceleration oF the particle at t f = 3 . 8 s. Correct answer: - 23 . 56 m / s 2 . Explanation: We can use the rules oF the di²erential calcu- lus to fnd the velocity From the displacement, at t = 3 . 8 s , the acceleration is a ( t ) = dv dt = d dt (42 . 8 m / s - 3 . 1 m / s 3 t 2 ) = - (2) (3 . 1 m / s 3 ) t = - (2) (3 . 1 m / s 3 ) (3 . 8 s) = - 23 . 56 m / s 2 . keywords: 003 (part 1 oF 2) 10 points An electron in the cathode ray tube oF a tele- vision set enters a region where it acceler- ates uniFormly From a speed oF 32000 m / s to a speed oF 3 . 08 × 10 6 m / s in a distance oF 3 . 84 cm. What is its acceleration?
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Homework_02 - Nguyen, Thanh Homework 2 Due: Sep 7 2007,...

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