Problem A uniform horizontal beam 5.00 m long and weighting 3.00 × 102 N is attached to a wall by a pin connection that allows the beam to rotate. Its far end is supported by a cable that makes an angle of 53.0° with the horizontal (Fig. 8.12a). If a person weighing 6.00 × 102 N stands 1.50 m from the wall, find the magnitude of the tension T in the cable and the force R exerted by the wall on the beam. R 53.0 300 N 600 N (b) R, T sin 53.0° R T cos 53.0° 53.0% 4.50 m→ 300 N 2.50 m- 600 N 5.00 m (a) (c)

College Physics
11th Edition
ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter1: Units, Trigonometry. And Vectors
Section: Chapter Questions
Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...
icon
Related questions
Question
**Solution**

From Figure 8.12, the forces causing torques are the wall force \(\vec{R}\), the gravity forces on the beam and the man, \(w_B\) and \(w_M\), and the tension force \(\vec{T}\). Apply the condition of rotational equilibrium.

Compute torques around the pin at \(O\), so \(\tau_R = 0\) (zero moment arm). The torque due to the beam’s weight acts at the beam’s center of gravity.

Substitute \(L = 5.00 \, \text{m}\) and the weights, solving for \(T\).

\[
\sum \tau_i = \tau_R + \tau_B + \tau_M + \tau_T = 0
\]

\[
\sum \tau_i = 0 - w_B(L/2) - w_M(1.50 \, \text{m}) + TL \sin(53.0^\circ) = 0
\]

\[
-(3.00 \times 10^2 \, \text{N})(2.5 \, \text{m}) - (6.00 \times 10^2 \, \text{N})(1.50 \, \text{m}) + (T \sin 53.0^\circ)(5.00 \, \text{m}) = 0
\]

\[ T = \underline{\hspace{2cm}} \, \text{N} \]

Now apply the first condition of equilibrium to the beam.

Substituting the value of \(T\) found in the previous step and the weights, obtain the components of \(\vec{R}\).

\[
\sum F_X = R_X + T \cos 53.0^\circ = 0 \quad (2)
\]

\[
\sum F_Y = R_Y - w_B - w_M + T \sin 53.0^\circ = 0 \quad (2)
\]

\[ R_X = \underline{\hspace{2cm}} \, \text{N} \]

\[ R_Y = \underline{\hspace{2cm}} \, \text{N} \]

---

**Remarks** 
Even if we selected some other axis for the torque equation, the solution would be the same. For example, if the axis were to pass
Transcribed Image Text:**Solution** From Figure 8.12, the forces causing torques are the wall force \(\vec{R}\), the gravity forces on the beam and the man, \(w_B\) and \(w_M\), and the tension force \(\vec{T}\). Apply the condition of rotational equilibrium. Compute torques around the pin at \(O\), so \(\tau_R = 0\) (zero moment arm). The torque due to the beam’s weight acts at the beam’s center of gravity. Substitute \(L = 5.00 \, \text{m}\) and the weights, solving for \(T\). \[ \sum \tau_i = \tau_R + \tau_B + \tau_M + \tau_T = 0 \] \[ \sum \tau_i = 0 - w_B(L/2) - w_M(1.50 \, \text{m}) + TL \sin(53.0^\circ) = 0 \] \[ -(3.00 \times 10^2 \, \text{N})(2.5 \, \text{m}) - (6.00 \times 10^2 \, \text{N})(1.50 \, \text{m}) + (T \sin 53.0^\circ)(5.00 \, \text{m}) = 0 \] \[ T = \underline{\hspace{2cm}} \, \text{N} \] Now apply the first condition of equilibrium to the beam. Substituting the value of \(T\) found in the previous step and the weights, obtain the components of \(\vec{R}\). \[ \sum F_X = R_X + T \cos 53.0^\circ = 0 \quad (2) \] \[ \sum F_Y = R_Y - w_B - w_M + T \sin 53.0^\circ = 0 \quad (2) \] \[ R_X = \underline{\hspace{2cm}} \, \text{N} \] \[ R_Y = \underline{\hspace{2cm}} \, \text{N} \] --- **Remarks** Even if we selected some other axis for the torque equation, the solution would be the same. For example, if the axis were to pass
**Example 8.7 Walking a Horizontal Beam**

**Goal**  
Solve an equilibrium problem with nonperpendicular torques.

**Problem**  
A uniform horizontal beam 5.00 m long and weighing 3.00 × 10² N is attached to a wall by a pin connection that allows the beam to rotate. Its far end is supported by a cable that makes an angle of 53.0° with the horizontal (Fig. 8.12a). If a person weighing 6.00 × 10² N stands 1.50 m from the wall, find the magnitude of the tension \(\vec{T}\) in the cable and the force \(\vec{R}\) exerted by the wall on the beam.

**Figure 8.12**

- **(a)** A uniform beam attached to a wall and supported by a cable.
- **(b)** A free-body diagram for the beam.
- **(c)** The component of the free-body diagram.

**Diagrams Explanation**

- **(a)** Illustrates a side view of the setup, showing the beam attached to the wall with a cable making a 53.0° angle. A person stands on the beam, 1.50 m away from the wall.
- **(b)** Displays the forces acting on the beam: the person's weight (600 N), the beam's weight (300 N), and the tension (\(\vec{T}\)) and reaction force (\(\vec{R}\)) vectors.
- **(c)** Breaks down the forces into components based on the angle: \(T \sin 53.0°\) and \(T \cos 53.0°\). Reaction forces from the wall are labeled as \(R_x\) and \(R_y\).

**Strategy**  
The second condition of equilibrium, \(\Sigma \tau_i = 0\), with torques computed around the pin, can be solved for the tension \(T\) in the cable. The first condition of equilibrium, \(\Sigma \vec{F}_i = 0\), gives two equations and two unknowns for the two components of the force exerted by the wall, \(R_x\) and \(R_y\).
Transcribed Image Text:**Example 8.7 Walking a Horizontal Beam** **Goal** Solve an equilibrium problem with nonperpendicular torques. **Problem** A uniform horizontal beam 5.00 m long and weighing 3.00 × 10² N is attached to a wall by a pin connection that allows the beam to rotate. Its far end is supported by a cable that makes an angle of 53.0° with the horizontal (Fig. 8.12a). If a person weighing 6.00 × 10² N stands 1.50 m from the wall, find the magnitude of the tension \(\vec{T}\) in the cable and the force \(\vec{R}\) exerted by the wall on the beam. **Figure 8.12** - **(a)** A uniform beam attached to a wall and supported by a cable. - **(b)** A free-body diagram for the beam. - **(c)** The component of the free-body diagram. **Diagrams Explanation** - **(a)** Illustrates a side view of the setup, showing the beam attached to the wall with a cable making a 53.0° angle. A person stands on the beam, 1.50 m away from the wall. - **(b)** Displays the forces acting on the beam: the person's weight (600 N), the beam's weight (300 N), and the tension (\(\vec{T}\)) and reaction force (\(\vec{R}\)) vectors. - **(c)** Breaks down the forces into components based on the angle: \(T \sin 53.0°\) and \(T \cos 53.0°\). Reaction forces from the wall are labeled as \(R_x\) and \(R_y\). **Strategy** The second condition of equilibrium, \(\Sigma \tau_i = 0\), with torques computed around the pin, can be solved for the tension \(T\) in the cable. The first condition of equilibrium, \(\Sigma \vec{F}_i = 0\), gives two equations and two unknowns for the two components of the force exerted by the wall, \(R_x\) and \(R_y\).
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps with 2 images

Blurred answer
Knowledge Booster
Torque
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.
Similar questions
  • SEE MORE QUESTIONS
Recommended textbooks for you
College Physics
College Physics
Physics
ISBN:
9781305952300
Author:
Raymond A. Serway, Chris Vuille
Publisher:
Cengage Learning
University Physics (14th Edition)
University Physics (14th Edition)
Physics
ISBN:
9780133969290
Author:
Hugh D. Young, Roger A. Freedman
Publisher:
PEARSON
Introduction To Quantum Mechanics
Introduction To Quantum Mechanics
Physics
ISBN:
9781107189638
Author:
Griffiths, David J., Schroeter, Darrell F.
Publisher:
Cambridge University Press
Physics for Scientists and Engineers
Physics for Scientists and Engineers
Physics
ISBN:
9781337553278
Author:
Raymond A. Serway, John W. Jewett
Publisher:
Cengage Learning
Lecture- Tutorials for Introductory Astronomy
Lecture- Tutorials for Introductory Astronomy
Physics
ISBN:
9780321820464
Author:
Edward E. Prather, Tim P. Slater, Jeff P. Adams, Gina Brissenden
Publisher:
Addison-Wesley
College Physics: A Strategic Approach (4th Editio…
College Physics: A Strategic Approach (4th Editio…
Physics
ISBN:
9780134609034
Author:
Randall D. Knight (Professor Emeritus), Brian Jones, Stuart Field
Publisher:
PEARSON