Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 9 - Section 9.1 - Vectors in Two Dimensions - 9.1 Exercises - Page 639: 74

Answer

$\vec {T_1} \approx-14115i+5783j$ and $\vec {T_2} \approx14115i+12495j$.

Work Step by Step

Step 1. Identify the vector for the weight as $\vec {W} =-18278j$ Step 2. Identify the vector for T1 as $\vec {T_1} =-T_1cos22.3^{\circ} i +T_1sin22.3^{\circ} j\approx-0.925T_1i +0.379T_1 j$ Step 3. Identify the vector for T2 as $\vec {T_2} =T_2cos41.5^{\circ} i +T_2sin41.5^{\circ} j\approx0.749T_2i +0.663T_2 j$ Step 4. For a balanced force, the total should be zero which gives $\vec {W} +\vec {T_1} +\vec {T_2} =0$ and this leads to $0.749T_2=0.925T_1$ (or $T_2=1.235T_1$) and $0.379T_1+0.663T_2=18278$ Step 5. Plug-in the first equation into the second one, we get $0.379T_1+0.663\times1.235T_1=18278$ which gives $T_1=15259.58lb$, and we also get $T_2=18845.58lb$ Step 6. Rewrite the above vectors as: $\vec {T_1} \approx-14115i+5783j$ and $\vec {T_2} \approx14115i+12495j$.
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