This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: narainswamy (ann452) HW2 Mackie (20211) 1 This printout should have 17 questions. Multiplechoice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 2) 10.0 points A speeder passes a parked police car at a constant speed of 34 . 5 m / s. At that instant, the police car starts from rest with a uniform acceleration of 2 . 08 m / s 2 . How much time passes before the speeder is overtaken by the police car? Correct answer: 33 . 1731 s. Explanation: Let : v = 34 . 5 m / s and a = 2 . 08 m / s 2 . x = v i t + 1 2 a t 2 Since the speeder has no acceleration, his position is given by x s = v t . The policeman starts from rest, so x p = 1 2 a t 2 . The cop overtakes the speeder when x s = x p v t = 1 2 a t 2 0 = a t 2 2 v t 0 = ( a t 2 v ) t t = 2 v a = 2 (34 . 5 m / s) 2 . 08 m / s 2 = 33 . 1731 s . 002 (part 2 of 2) 10.0 points How far does the speeder travel before being overtaken by the police car? Correct answer: 1144 . 47 m. Explanation: The distance may be obtained with either d = v t = (34 . 5 m / s) (33 . 1731 s) = 1144 . 47 m or d = 1 2 a t 2 = 1 2 ( 2 . 08 m / s 2 ) (33 . 1731 s) 2 = 1144 . 47 m . 003 (part 1 of 2) 10.0 points A stone falls from rest from the top of a cliff. A second stone is thrown downward from the same height 3 s later with an initial speed of 58 . 8 m / s. They hit the ground at the same time. The acceleration of gravity is 9 . 8 m / s 2 . How long does it take the first stone to hit the ground? Correct answer: 4 . 5 s. Explanation: For stone 1: y 1 = 1 2 g t 2 1 For stone 2: y 2 = v t 2 + g t 2 2 2 Stone 2 is thrown t seconds after stone 1 and they hit the ground at the same time, so t 1 = t 2 + t . Since the height of the cliff is the same for both of the stones, y 1 = y 2 g t 2 1 2 = v ( t 1 t ) + g 2 ( t 1 t ) 2 ( v g t ) t 1 = v t g 2 t 2 t 1 = v t g 2 t 2 v g t = (58 . 8 m / s) (3 s) (58 . 8 m / s) (9 . 8 m / s 2 ) (3 s) (9 . 8 m / s 2 ) 2 (3 s) 2 (58 . 8 m / s) (9 . 8 m / s 2 ) (3 s) = 4 . 5 s . narainswamy (ann452) HW2 Mackie (20211)...
View
Full
Document
 Spring '09
 MACKIE
 Physics, Work

Click to edit the document details