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Unformatted text preview: net the strength of the magnetic field decreases. As the length of the wire increases, the magnetic field experienced by the ends of the wire decreases in strength, leading to a smaller magnetic force than expected. 1 point 1 point 1 point 1 point 2008 The College Board. All rights reserved. Visit the College Board on the Web: www.collegeboard.com. AP PHYSICS B 2008 SCORING GUIDELINES
Question 4
10 points total Distribution of points (a) 3 points For a correct application of kinematics to the vertical motion 2 2 u yf = u y 0  2 gh = 0
2 u y 0 = 2 gh 1 point For correctly expressing the vertical component of the initial velocity u y 0 = u0 sin 50 For a correct solution u0 sin 50 = 2gh
2 gh u0 = = sin 50 1 point 1 point 2 9.8 m s2 ( 0.150 m ) sin 50 ( ) u0 = 2.24 m s (or 2.26 m s using g = 10 m s2 ) (b) 2 points For a correct expression for the volume flow rate, using an area of p r02
Volume flow rate = A0u0 = pr02u0 1 point For a correct solution with correct units, consistent with u0 found in part (a) 1 point Volume flow rate = p 4.00 103 m ( ) 2 (2.24 m s) Volume flow rate = 1.13 10 4 m3 s (or 1.14 10 4 m3 s using g = 10 m s2 ) 2008 The College Board. All rights reserved. Visit the College Board on the Web: www.collegeboard.com. AP PHYSICS B 2008 SCORING GUIDELINES
Question 4 (continued)
Distribution of points (c) 5 points For a correct expression for the water velocity in the feeder pipe with substitutions consistent with previous work A0u0 = Apu p 1 point r ^ A 4.00 10 3 m ^ 2.24 m s u p = 0 u0 = 0 ~ u0 = Ap 7.00 10 3 m ~ rp For a correctly calculated answer consistent with previous work
u p = 0.731 m s (or u p = 0.738 m s using g = 10 m s )
2 2 2 1 point 1 point For a correct expression of Bernoulli's equation 1 2 1 P0 + rgh0 + ru0 = Pp + rgh p + ru 2 2 2 p 1 2 Pp  P0 = rg h0  h p + r u0  u 2 p 2 For consistent/correct substitutions of heights and velocities Pp  P0 = 1.0 103 kg m3 9.8 m s2 (3.00 m ) ( ) ( ) ( 1 2 2 1.0 103 kg m 3 (2.24 m s)  (0.731 m s)...
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This note was uploaded on 02/09/2011 for the course PHYS 10 taught by Professor Davidnewton during the Spring '11 term at DeAnza College.
 Spring '11
 DavidNewton
 Physics

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