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Unformatted text preview: roofner (bar784) – Homework 2 – Weathers – (17104) 1 This printout should have 10 questions. Multiplechoice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 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 = 40 . 7 m / s, β = 5 . 37 m / s 3 , and t is in seconds. Find the average acceleration in the time interval from t = 0 to 3 . 77 s. Correct answer: 20 . 2449 m / s 2 . Explanation: The velocities at t i = 0 and t f = 3 . 77 s are found by substituting these values into the expression given for the velocity: v i = ( α β t 2 i ) = (40 . 7 m / s (5 . 37 m / s 3 ) (0 s) 2 ) = 40 . 7 m / s , v f = ( α β t 2 f ) = (40 . 7 m / s (5 . 37 m / s 3 ) (3 . 77 s) 2 ) = 35 . 6233 m / s . Therefore, the average acceleration in the specified time interval Δ t = t f t i = 3 . 77 s is ¯ a = v f v i t f t i = 35 . 6233 m / s 40 . 7 m / s 3 . 77 s 0 s = 20 . 2449 m / s 2 . 002 (part 2 of 2) 10.0 points Determine the acceleration of the particle at t f = 3 . 77 s. Correct answer: 40 . 4898 m / s 2 . Explanation: We can use the rules of the differential calcu lus to find the velocity from the displacement, at t = 3 . 77 s , the acceleration is a ( t ) = d v d t = d d t (40 . 7 m / s 5 . 37 m / s 3 t 2 ) = (2) (5 . 37 m / s 3 ) t = (2) (5 . 37 m / s 3 ) (3 . 77 s) = 40 . 4898 m / s 2 . 003 (part 1 of 2) 10.0 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 42200 m / s to a speed of 3 . 42 × 10 6 m / s in a distance of 3 . 25 cm....
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This document was uploaded on 10/26/2011 for the course PHYS 1710 at North Texas.
 Fall '08
 Weathers
 mechanics, Work

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