The second photo has background info to help solve the practice problem Page 111 Practice Problem 4.7: The weight of the reflector (the earth's gravitational pull) andthe force the reflector exerts on the earth form an action-reaction pair. Determine themagnitude and direction of each of these forces. Answers: 1960 N up. ban6. Check to make sure that your forces beythe direction of the net force, make sure that its direction is the same as that of theacceleration, as required by Newton's second law.westeroch Later (in Chapter 5), we'll expand this strategy to deal with more complex problems,but it's important for you to use it consistently from the very start, to develop good hab-its in the systematic analysis of problems.EXAMPLE 4.7 Tension in a massless chainNow let's apply our problem-solving strategy to a system in equilibrium. To improve the acoustics in anauditorium, a sound reflector with a mass of 200 kg is suspended by a chain from the ceiling. What is itsweight? What force (magnitude and direction) does the chain exert on it? What is the tension in the chain?Assume that the mass of the chain itself is negligible.SOLUTIONSET UP The reflector is in equilibrium, so we use Newton's first law,EF = 0. We draw separate free-body diagrams for the reflector andthe chain (Figure 4.26). We take the positive y axis to be upward, asshown. Each force has only a y component. We give symbolic labels tothe magnitudes of the unknown forces, using T to represent the tensionin the chain.SOLVE The magnitude of the weight w of the reflector is given byEquation 4.9:w = mg = (200 kg) (9.80 m/s²) = 1960 N.Armed with this number and Newton's first law, we can compute theunknown force magnitudes.Video Tutor SolutionThe weight of the reflector is a force pointing in the -y direction,so its y component is -1960 N. The upward force 7 exerted on the re-flector by the chain has unknown magnitude T. Because the reflector isin equilibrium, the sum of the y components of force on it must be zero:ΣF, T+ (-1960 N) = 0,T = 1960 N.SOThe chain pulls up on the reflector with a force 7 of magnitude 1960 N.By Newton's third law, the reflector pulls down on the chain with aforce of magnitude 1960 N.The chain is also in equilibrium, so the vector sum of forces onit must equal zero. For this to be true, an upward force with magni-tude 1960 N must act on it at its top end. The tension in the chain isT= 1960 N.CONTINUED

Given data:- mass of the reflector (m)=200kg Weight of the chain is neglected To find:- Weight of…

Page 111 Practice Problem 4.7: The weight of the reflector (the earth's gravitational pull) and the force the reflector exerts on the earth form an action-reaction magnitude and direction of each of these forces. Answers: 1960 N up. pair. Determine the

Page 111 Practice Problem 4.7: The weight of the reflector (the earth's gravitational pull) and the force the reflector exerts on the earth form an action-reaction magnitude and direction of each of these forces. Answers: 1960 N up. pair. Determine the

International Edition---engineering Mechanics: Statics, 4th Edition

4th Edition

ISBN:9781305501607

Author:Andrew Pytel And Jaan Kiusalaas

Publisher:Andrew Pytel And Jaan Kiusalaas

Chapter5: Three-dimensional Equilibrium

Section: Chapter Questions

Problem 5.39P: The bent rod of negligible weight is supported by the ball-and-socket joint at B and the cables...

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