physics hmwk 2 solution - kim (sk29727) – HW #2 – lewis...

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Unformatted text preview: kim (sk29727) – HW #2 – lewis – (81437) 1 This print-out should have 47 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. Chapter 2 001 (part 1 of 2) 10.0 points Two points have cartesian coordinates (7 m ,- 10 m) and (- 10 m , 6 . 1 m). Find the distance between these points. Correct answer: 23 . 4139 m. Explanation: Let : x 1 = 7 m , y 1 =- 10 m , x 2 =- 10 m , and y 2 = 6 . 1 m . The distance is d = radicalBig ( x 2- x 1 ) 2 + ( y 2- y 1 ) 2 = { [- 10 m- (7 m)] 2 + [6 . 1 m- (- 10 m)] 2 } 1 / 2 = 23 . 4139 m . 002 (part 2 of 2) 10.0 points What is the angle between the line connect- ing the two points and the x-axis (measured counter-clockwise from the x-axis and within the limits of- 180 ◦ to +180 ◦ )? Correct answer: 136 . 558 ◦ . Explanation: The angle is θ = arctan parenleftbigg y 2- y 1 x 2- x 1 parenrightbigg = arctan bracketleftbigg 6 . 1 m- (- 10 m)- 10 m- (7 m) bracketrightbigg = 136 . 558 ◦ . (- 10, 6 . 1) (7,- 10) θ 003 (part 1 of 2) 10.0 points A physics book is moved once around the perimeter of a table of dimensions 1 m by 3 m. If the book ends up at its initial position, what is the magnitude of its displacement? 1. 0 m correct 2. 8 m 3. 3 m 4. 1 m 5. 6 m 6. 5 m 7. None of these 8. 4 m 9. 7 m 10. 2 m Explanation: Since its final position is the same as its initial position, the displacement is 0. kim (sk29727) – HW #2 – lewis – (81437) 2 004 (part 2 of 2) 10.0 points What is the distance traveled? 1. 6 m 2. 3 m 3. 1 m 4. 8 m correct 5. 4 m 6. None of these 7. 7 m 8. 5 m 9. 2 m 10. 0 m Explanation: The distance traveled is the perimeter of the table: d = 2 ℓ + 2 w = 2 (1 m) + 2 (3 m) = 8 m . 005 10.0 points A rocket initially at rest accelerates at a rate of 50 m / s 2 for 0 . 21 min. What is its speed at the end of this time? Correct answer: 630 m / s. Explanation: Let : a = 50 m / s 2 and t = 0 . 21 min . v f = v o + a t = a t = (50 m / s 2 ) (0 . 21 min) 60 s 1 min = 630 m / s . 006 10.0 points Two ants race across a table 75 cm long. One travels at 4 . 32 cm / s and the other at 2 cm / s. When the first one crosses the finish line, how far behind is the second one? Correct answer: 40 . 2778 cm. Explanation: Let : ℓ = 75 cm , v 1 = 4 . 32 cm / s , and v 2 = 2 cm / s . The time it takes the first (faster) ant to cross the finish line is t = ℓ v 1 , and the distance the slower ant covers in that time is s 2 = v 2 t = v 2 ℓ v 1 . The slower ant is ℓ- s 2 = ℓ- v 2 ℓ v 1 = 75 cm- (2 cm / s) (75 cm) 4 . 32 cm / s = 40 . 2778 cm from the finish line when the faster one crosses it. 007 (part 1 of 2) 10.0 points You drive a car 5 h at 50 km / h, then 5 h at 68 km / h....
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This note was uploaded on 11/03/2010 for the course PHYS 1441 taught by Professor Teacher during the Spring '10 term at Abilene Christian University.

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physics hmwk 2 solution - kim (sk29727) – HW #2 – lewis...

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