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Unformatted text preview: CHAPTER 1 1.1. Given the vectors M = 10 a x + 4 a y 8 a z and N = 8 a x + 7 a y 2 a z , find: a) a unit vector in the direction of M + 2 N . M + 2 N = 10 a x 4 a y + 8 a z + 16 a x + 14 a y 4 a z = ( 26 , 10 , 4 ) Thus a = ( 26 , 10 , 4 )  ( 26 , 10 , 4 )  = ( . 92 , . 36 , . 14 ) b) the magnitude of 5 a x + N 3 M : ( 5 , , ) + ( 8 , 7 , 2 ) ( 30 , 12 , 24 ) = ( 43 , 5 , 22 ) , and  ( 43 , 5 , 22 )  = 48 . 6 . c)  M  2 N  ( M + N ) :  ( 10 , 4 , 8 )  ( 16 , 14 , 4 )  ( 2 , 11 , 10 ) = ( 13 . 4 )( 21 . 6 )( 2 , 11 , 10 ) = ( 580 . 5 , 3193 , 2902 ) 1.2. Given three points, A( 4 , 3 , 2 ) , B( 2 , , 5 ) , and C( 7 , 2 , 1 ) : a) Specify the vector A extending from the origin to the point A . A = ( 4 , 3 , 2 ) = 4 a x + 3 a y + 2 a z b) Give a unit vector extending from the origin to the midpoint of line AB . The vector from the origin to the midpoint is given by M = ( 1 / 2 )( A + B ) = ( 1 / 2 )( 4 2 , 3 + , 2 + 5 ) = ( 1 , 1 . 5 , 3 . 5 ) The unit vector will be m = ( 1 , 1 . 5 , 3 . 5 )  ( 1 , 1 . 5 , 3 . 5 )  = ( . 25 , . 38 , . 89 ) c) Calculate the length of the perimeter of triangle ABC : Begin with AB = ( 6 , 3 , 3 ) , BC = ( 9 , 2 , 4 ) , CA = ( 3 , 5 , 1 ) . Then  AB  +  BC  +  CA  = 7 . 35 + 10 . 05 + 5 . 91 = 23 . 32 1.3. The vector from the origin to the point A is given as ( 6 , 2 , 4 ) , and the unit vector directed from the origin toward point B is ( 2 , 2 , 1 )/ 3. If points A and B are ten units apart, find the coordinates of point B . With A = ( 6 , 2 , 4 ) and B = 1 3 B( 2 , 2 , 1 ) , we use the fact that  B A  = 10, or  ( 6 2 3 B) a x ( 2 2 3 B) a y ( 4 + 1 3 B) a z  = 10 Expanding, obtain 36 8 B + 4 9 B 2 + 4 8 3 B + 4 9 B 2 + 16 + 8 3 B + 1 9 B 2 = 100 or B 2 8 B 44 = 0. Thus B = 8 64 176 2 = 11 . 75 (taking positive option) and so B = 2 3 ( 11 . 75 ) a x 2 3 ( 11 . 75 ) a y + 1 3 ( 11 . 75 ) a z = 7 . 83 a x 7 . 83 a y + 3 . 92 a z 1 1.4. given points A( 8 , 5 , 4 ) and B( 2 , 3 , 2 ) , find: a) the distance from A to B .  B A  =  ( 10 , 8 , 2 )  = 12 . 96 b) a unit vector directed from A towards B . This is found through a AB = B A  B A  = ( . 77 , . 62 , . 15 ) c) a unit vector directed from the origin to the midpoint of the line AB . a M = ( A + B )/ 2  ( A + B )/ 2  = ( 3 , 1 , 3 ) 19 = ( . 69 , . 23 , . 69 ) d) the coordinates of the point on the line connecting A to B at which the line intersects the plane z = 3. Note that the midpoint, ( 3 , 1 , 3 ) , as determined from part c happens to have z coordinate of 3. This is the point we are looking for. 1.5. A vector field is specified as G = 24 xy a x + 12 (x 2 + 2 ) a y + 18 z 2 a z . Given two points, P( 1 , 2 , 1 ) and Q( 2 , 1 , 3 ) , find: a) G at P : G ( 1 , 2 , 1 ) = ( 48 , 36 , 18 ) b) a unit vector in the direction of G at Q : G ( 2 , 1 , 3 ) = ( 48 , 72 , 162 ) , so a G = ( 48 , 72 , 162 )  ( 48 , 72 , 162 )  = ( . 26 , . 39 , . 88 ) c) a unit vector directed from Q toward P : a QP = P Q  P Q  = ( 3 , 1 , 4 ) 26 = ( . 59 , . 20 , . 78 ) d) the equation of the surface on which  G  = 60: We write 60 =  ( 24 xy, 12 (x 2 + 2 ), 18 z 2 )  , or 10 =  ( 4 xy, 2 x 2 + 4 , 3 z 2 )  , so the equation is 100 = 16 x 2 y 2 + 4 x 4 + 16 x 2 + 16 + 9 z 4 2 1.6. For the G field in Problem 1.5, make sketches of G x , G y , G z and  G  along the line y = 1, z = 1, for x 2. We find G (x, 1 , 1 ) = ( 24 x, 12 x 2 + 24 , 18 ) , from which G x = 24 x , G y = 12 x 2 + 24, G z = 18, and  G  = 6 4 x 4 + 32 x 2 + 25. Plots are shown below....
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This note was uploaded on 06/10/2008 for the course EE 325 taught by Professor Brown during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Brown
 Electromagnet

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