S04s(3) - Physics 4A FINAL EXAM Chapters 1 - 15 Spring 2004...

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Physics 4A FINAL EXAM Chapters 1 - 15 Spring 2004 1 Name:________________________________________ Posting Code _____ _____ _____ Solve the following problems in the space provided. Use the back of the page if needed. Each problem is worth 10 points. You must show your work in a logical fashion starting with the correctly applied physical principles which are on the last page. Your score will be maximized if your work is easy to follow because partial credit will be awarded. 1. A firefighter 9.00m from a building directs a stream of water from a hose moving at 10.0m/s at an angle of 53.0˚ above the horizontal. Find (a)the time between when the water leaves the hose and it reaches the building and (b)the height at which the water strikes the building. (a)Use the kinematic equation for x, x = x o + v ox t + 1 2 a x t 2 " x = v t " t = x v Putting in the numbers, t = 9.00 6.00 " t = 1.50 s . (b)Use the kinematic equation for y, y = y o + v oy t + 1 2 a y t 2 " y = 0 + (8.00)(1.50) # 1 2 (9.80)(1.50) 2 Finally, y = 0.975 m . 2. A 95.5N board is sandwiched between to other boards as shown. The coefficient of friction between the boards is 0.663. (a)Draw the forces that act on the 95.5N board. (b)Find the magnitude of each force. Applying Newton’s Second Law, " F x = ma x # F n 1 $ F n 2 = 0 # F n 1 = F n 2 " F y = y # F f 1 + F f 2 $ F g = 0 " F f 1 + F f 2 = F g Using the definition of COF, F f 1 = μ F n 1 and F f 2 = F n 2 . Plugging into the equation from the y-direction, F n 1 + F n 2 = F g " F n 1 + F n 2 ( )= F g . x o = 0 x = 9.00m v ox = 10.0cos53˚= 6.00m/s v x = 6.00m/s a x = 0 t = ? y o = 0 y = ? v oy = 10.0sin53˚= 8.00m/s v y = ? 2 θ x y F g = 95.5N F f2 F f1 F n2 F n1 x y
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Physics 4A FINAL EXAM Chapters 1 - 15 Spring 2004 2 Since the normal forces are equal, 2 μ F n 1 = F g " F n 1 = F g 2 = 95.5 2(0.663) " F n 1 = F n 2 = 72.0 N . The frictional forces must also be equal, F f 1 = F f 2 = F n 1 = (0.663)(72.0) " F f 1 = F f 2 = 47.7 N .
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Physics 4A FINAL EXAM Chapters 1 - 15 Spring 2004 3 3. A 400g ball is attached to a vertical rod by two strings as shown. The ball rotates in a horizontal circle at 6.00m/s. Find the tension in each string.
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S04s(3) - Physics 4A FINAL EXAM Chapters 1 - 15 Spring 2004...

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