/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 20 A nonuniform beam 4.50 \(\mathrm... [FREE SOLUTION] | 91Ó°ÊÓ

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A nonuniform beam 4.50 \(\mathrm{m}\) long and weighing 1.00 \(\mathrm{kN}\) makes an angle of \(25.0^{\circ}\) below the horizontal. It is held in position by a frictionless pivot at its upper right end and by a cable 3.00 \(\mathrm{m}\) farther down the beam and perpendicular to it (Fig. 11.31\()\) . The center of gravity of the beam is 2.00 \(\mathrm{m}\) down the beam from the pivot. Lighting equipment exerts a \(5.00-\mathrm{kN}\) downward force on the lower left endof the beam. Find the tension \(T\) in the cable and the horizontal and vertical components of the force exerted on the beam by the pivot. Start by sketching a free-body diagram of the beam.

Short Answer

Expert verified
Tension in the cable is 7.59 kN. Horizontal force at the pivot is 3.19 kN, vertical force is 1.58 kN.

Step by step solution

01

Free-Body Diagram

Begin by sketching the beam. The pivot is at the upper right end, the cable is attached 3.00 m from the pivot, and the center of gravity is 2.00 m from the pivot. The forces acting are the tension in the cable (T), the weight of the beam (1.00 kN), and a 5.00 kN downward force at the left end of the beam. The angle below the horizontal is 25.0 degrees.
02

Resolve Forces

The forces acting on the beam include the tension T in the cable and the forces at the pivot both horizontal (F_h) and vertical (F_v). The weight of the beam acts downward at its center of gravity and the 5.00 kN force acts downward at the left end.
03

Calculate Torque

Use the pivot point to calculate torques about the pivot. Set the sum of the torques to zero since the beam is in equilibrium:\[ T imes 3.00 = 1.00 \times 2.00 \times \cos(25.0) + 5.00 \times 4.50 \times \cos(25.0) \]Solve for tension T.
04

Solve for Tension T

Substitute the known values and solve for T:\[ T \times 3.00 = 1.00 \times 2.00 \times \cos(25.0) + 5.00 \times 4.50 \times \cos(25.0) \]Calculate T = 7.59 kN.
05

Equilibrium of Forces

The sum of the forces in the horizontal direction must equal zero. This gives:\[ T \times \sin(25.0) = F_h \]Solve for the horizontal force F_h.
06

Solve for Horizontal Force F_h

Substitute T = 7.59 kN:\[ F_h = 7.59 \times \sin(25.0) = 3.19 \text{ kN} \]
07

Vertical Forces

The sum of the forces in the vertical direction must also equal zero. This gives:\[ F_v + T \times \cos(25.0) = 1.00 + 5.00 \]Solve for the vertical force F_v.
08

Solve for Vertical Force F_v

Substitute T = 7.59 kN:\[ F_v = 1.00 + 5.00 - 7.59 \times \cos(25.0) = 1.58 \text{ kN} \]

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Nonuniform Beam Mechanics
Nonuniform beam mechanics involves analyzing beams whose density varies along their length, impacting how forces are distributed. This exercise features a beam supported by a pivot, influenced by its own weight, and the applied force of lighting equipment. The center of gravity, notably 2.00 meters from the pivot, plays a critical role in calculations. Although the beam is structurally one piece, its nonuniformity means the weight doesn't act evenly along its length, leading to varied torque and force calculations.

Understanding how the weight varies along the beam helps in resolving forces and calculating tension, ensuring the beam is correctly balanced in a mechanical system. In this case, knowing where the center of gravity lies helps you anticipate which parts of the beam bear more force than others.
Torque Equilibrium
In physics, torque is force applied at a distance from a pivot point, causing rotation. For this beam to remain stationary, the sum of the torques around the pivot must be zero. This balance is known as torque equilibrium.

The formula used here was:
  • Torque caused by the cable's tension: \( T \times 3.00 \)
  • Torque from the beam's weight: \( 1.00 \times 2.00 \times \cos(25.0) \)
  • Torque from the lighting equipment: \( 5.00 \times 4.50 \times \cos(25.0) \)
Calculating these torques helps determine the necessary tension in the cable to counterbalance them, keeping the beam in equilibrium. This ensures that the beam neither rotates nor tilts but stays steady at its position, fulfilling its purpose safely.
Force Resolution
Force resolution is about breaking down forces into components that align with different axes. For the beam, identifying the tension and its horizontal and vertical components was crucial to maintaining equilibrium in this setup.
  • The cable force is resolved into horizontal (\( F_h \)) and vertical (\( F_v \)) directions using trigonometric functions.
  • Horizontal: \( T \times \sin(25.0) = F_h \)
  • Vertical: \( F_v + T \times \cos(25.0) = 1.00 + 5.00 \)
These components help calculate the correct counterforces needed at the pivot to keep the beam stable. By resolving tension into these components, you understand how it interacts with other forces acting on the system.
Free-Body Diagram
A free-body diagram is a visual tool used to show all forces acting upon an object, which in this exercise is the beam. It's essential to solving mechanics problems as it simplifies complex systems by highlighting only the forces and moments acting.
  • Start by drawing the beam based on given dimensions and inclinations.
  • Identify each force, like weight, tension, and external forces applied, using arrows for direction and point of application.
  • Consider the angle to break down the forces into horizontal and vertical components.
By starting with a sketch, you establish a clear reference for solving force and torque equations. This step is indispensable for systematically tackling equilibrium problems.
Equilibrium of Forces
Equilibrium in a mechanical system means all forces acting on the system cancel out, resulting in no net motion. For the beam, we are concerned with forces in both the horizontal and vertical directions.
  • In the horizontal: Each force must counterbalance in magnitude, so the sum is zero. This gives the equation: \( T \times \sin(25.0) = F_h \).
  • In the vertical: Forces include upward forces (tension's vertical component, pivot's force) and downward forces (weight, additional loads). These forces summed up to zero led to: \( F_v = 1.00 + 5.00 - T \times \cos(25.0) \).
The outcome is a state where neither rotation nor shifting occurs. Understanding these concepts ensures proper design and safety in engineering scenarios.

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Most popular questions from this chapter

A specimen of oil having an initial volume of 600 \(\mathrm{cm}^{3}\) is subjected to a pressure increase of \(3.6 \times 10^{5} \mathrm{Pa},\) and the volume is found to decrease by 0.45 \(\mathrm{cm}^{3} .\) What is the bulk modulus of the material? The compressibility?

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In constructing a large mobile, an artist hangs an aluminum sphere of mass 6.0 \(\mathrm{kg}\) from a vertical steel wire 0.50 \(\mathrm{m}\) long and \(2.5 \times 10^{-3} \mathrm{cm}^{2}\) in cross-sectional area. On the bottom of the sphere he attaches a similar steel wire, from which he hangs a brass cube of mass 10.0 \(\mathrm{kg}\) . For each wire, compute (a) the tensile strain and \((\mathrm{b})\) the elongation.

A metal wire 3.50 \(\mathrm{m}\) long and 0.70 \(\mathrm{mm}\) in diameter was given the following test. A load weighing 20 \(\mathrm{N}\) was originally hung from the wire to keep it taut. The position of the lower end of the wire was read on a scale as load was added. $$ \begin{array}{cc}{\text { Added Load (N) }} & {\text { Scale Reading (cm) }} \\\ \hline 0 & {3.02} \\ {10} & {3.07} \\ {20} & {3.12} \\ {30} & {3.17} \\\ {40} & {3.22} \\ {50} & {3.27} \\ {60} & {3.32} \\ {70} & {4.27}\end{array} $$ (a) Graph these values, plotting the increase in length horizontally and the added load vertically. \((b)\) Calculate the value of Young's modulus. (c) The proportional limit occurred at a scale reading of 3.34 \(\mathrm{cm} .\) What was the stress at this point?

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