BEDFORD ESTATICA
Enviado por alex19z • 20 de Marzo de 2013 • 412 Palabras (2 Páginas) • 668 Visitas
Problem 2.1 In Active Example 2.1, suppose that the
vectors U and V are reoriented as shown. The vector
V is vertical. The magnitudes are jUj D 8 and jVj D 3.
Graphically determine the magnitude of the vector
U C 2V.
U V
45
Solution: Draw the vectors accurately and measure the resultant.
R D jU C 2Vj D 5.7 R D 5.7
Problem 2.2 Suppose that the pylon in Example 2.2 is
moved closer to the stadium so that the angle between
the forces FAB and FAC is 50°. Draw a sketch of the
new situation. The magnitudes of the forces are jFABj D 100 kN and jFACj D 60 kN. Graphically determine the
magnitude and direction of the sum of the forces exerted
on the pylon by the cables.
Solution: Accurately draw the vectors and measure the magnitude
and direction of the resultant
jFAB C FACj D 146 kN
˛ D 32°
c 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they
currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher.
7
Problem 2.3 The magnitude jFAj D 80 lb and the
angle ˛ D 65°. The magnitude jFA C FBj D 120 lb.
Graphically determine the magnitude of FB.
FB
FA
a
FC
Solution: Accurately draw the vectors and measure the magnitude
of FB.
jFBj D 62 lb
Problem 2.4 The magnitudes jFAj D 40 N, jFBj D 50 N, and jFCj D 40 N. The angle ˛ D 50° and ˇ D 80°.
Graphically determine the magnitude of FA C FB C FC.
FB
FA
a
FC
Solution: Accurately draw the vectors and measure the magnitude
of FA C FB C FC.
R D jFA C FB C FCj D 83 N
8
c 2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they
currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher.
Problem 2.5 The magnitudes jFAj D jFBj D jFCj D 100 lb, and the angles ˛ D 30°. Graphically determine
the value of the angle ˇ for which the magnitude
jFA C FB C FCj is a minimum and the minimum value
of jFA C FB C FCj.
FB
FA
a
FC
Solution: For a minimum, the vector FC must point back to the
origin.
R D jFA C FB C FCj D 93.2 lb
ˇ D 165°
Problem 2.6 The angle D 50°. Graphically determine
the magnitude of the vector rAC. 60 mm 150 mm
A C
B
rAB rBC
rAC
Solution: Draw the vectors accurately and then measure jrACj.
...