1-D motion-solutions

1-D motion-solutions - le (txl65) 1-D motion mohanty...

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le (txl65) – 1-D motion – mohanty – (81440) 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points You are trying to fnd out how high you have to pitch a water balloon in order For it to burst when it hits the ground. You discover that the balloon bursts when you have pitched it to a height oF 18 m. With what velocity did the balloon hit the ground? The acceleration oF gravity is 9 . 8 m / s 2 . Correct answer: - 18 . 783 m / s. Explanation: Consider the second halF oF the motion with up positive: Let : v 0 = 0 m / s , Δ h = - 18 m , and g = - 9 . 8 m / s 2 . when the balloon was Falling From rest ( v 0 = 0 m/s) From the height h under the in±uence oF gravity. The fnal speed is given by v 2 f = v 2 0 + 2 g h = 2 g h v f = ± r 2 g h = ± R 2 ( - 9 . 8 m / s 2 ) ( - 18 m) = ± 18 . 783 m / s directed downward, so it is - 18 . 783 m / s . 002 (part 1 of 2) 10.0 points A golF ball is released From rest From the top oF a very tall building. Choose a coordinate system whose origin is at the starting point oF the ball, and whose y axis points vertically upward. Neglecting air resistance, calculate the ve- locity oF the ball aFter 3 . 19 s. The acceleration oF gravity is 9 . 8 m / s 2 . Correct answer: - 31 . 262 m / s. Explanation: Let : v 0 = 0 m / s , Δ t = 3 . 19 s , and g = - 9 . 8 m / s 2 . v f = v 0 + g t = g t = ( - 9 . 8 m / s 2 ) (3 . 19 s) = - 31 . 262 m / s , directed downward. 003 (part 2 of 2) 10.0 points What is the position oF the ball aFter 3 . 19 s? Neglect air resistance. Correct answer: - 49 . 8629 m. Explanation: Let : y 0 = 0 . y = 1 2 g t 2 = 1 2 ( - 9 . 8 m / s 2 ) (3 . 19 s) 2 = - 49 . 8629 m , directed downward. 004 (part 1 of 3) 10.0 points Two cars approach each other; both cars are moving westward, one at 75 km / h, the other at 51 km / h. What is the magnitude oF the velocity oF the frst car relative to (in the Frame oF reFerence oF) the second car? Correct answer: 24 km / h. Explanation: All the motion is directed westward, so we can consider west to be positive. The velocity oF the frst car relative to the second car is v r = v 1 - v 2 = 75 km / h - 51 km / h = 24 km / h .
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le (txl65) – 1-D motion – mohanty – (81440) 2 Alternate Solution: Let east be positive: The velocity of the Frst car relative to the second car is v r = v 1 - v 2 = - 75 km / h - ( - 51 km / h) = - 24 km / h , which has a magnitude of 24 km / h.
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1-D motion-solutions - le (txl65) 1-D motion mohanty...

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