Math Problem Statement

PHYSICS A 15 kg beam of length 8 m holding a 61 kg mass is attached by wire to a wall. The distance of mass m from the right end of the beam is 3 m. The rope makes an angle of 11 degrees from the horizontal. What is the vertical reaction at the hinge?( use g=9.8 m/s^2)

Solution

To calculate the vertical reaction at the hinge (RyR_y), we apply the principles of static equilibrium, which state that:

  1. The sum of all vertical forces is zero: Fy=0\sum F_y = 0

  2. The sum of all moments about any point is zero: τ=0\sum \tau = 0

Step-by-Step Solution:

Step 1: Forces acting on the system

  1. Weight of the beam: Wbeam=mbeamg=159.8=147NW_{\text{beam}} = m_{\text{beam}} \cdot g = 15 \cdot 9.8 = 147 \, \text{N} This force acts at the center of the beam, which is 8/2=4m8/2 = 4 \, \text{m} from the hinge.

  2. Weight of the hanging mass: Wmass=mmassg=619.8=597.8NW_{\text{mass}} = m_{\text{mass}} \cdot g = 61 \cdot 9.8 = 597.8 \, \text{N} This force acts 83=5m8 - 3 = 5 \, \text{m} from the hinge (to the left).

  3. Tension in the rope (TT):
    The tension acts at an angle of 1111^\circ to the horizontal. This tension has both vertical and horizontal components:

    • Vertical component: Ty=Tsin(11)T_y = T \sin(11^\circ)
    • Horizontal component: Tx=Tcos(11)T_x = T \cos(11^\circ)
  4. Reaction forces at the hinge: The hinge provides two reaction forces:

    • Horizontal reaction: RxR_x
    • Vertical reaction: RyR_y

Step 2: Write the equilibrium equations

  1. Vertical forces equilibrium: Ry+Ty=Wbeam+WmassR_y + T_y = W_{\text{beam}} + W_{\text{mass}} Ry+Tsin(11)=147+597.8R_y + T \sin(11^\circ) = 147 + 597.8 R_y + T \sin(11^\circ) = 744.8 \, \text{N} \tag{1}

  2. Moments equilibrium about the hinge: Taking moments about the hinge (τhinge=0\sum \tau_{\text{hinge}} = 0):

    • Clockwise moments: Wbeam4+Wmass5W_{\text{beam}} \cdot 4 + W_{\text{mass}} \cdot 5
    • Counterclockwise moment: Ty8=Tsin(11)8T_y \cdot 8 = T \sin(11^\circ) \cdot 8 Equating clockwise and counterclockwise moments: Tsin(11)8=1474+597.85T \sin(11^\circ) \cdot 8 = 147 \cdot 4 + 597.8 \cdot 5 Tsin(11)8=588+2989T \sin(11^\circ) \cdot 8 = 588 + 2989 Tsin(11)8=3577NmT \sin(11^\circ) \cdot 8 = 3577 \, \text{N} \cdot \text{m} Tsin(11)=35778=447.125NT \sin(11^\circ) = \frac{3577}{8} = 447.125 \, \text{N} T=447.125sin(11)T = \frac{447.125}{\sin(11^\circ)} Using sin(11)0.1908\sin(11^\circ) \approx 0.1908: T=447.1250.19082343.6NT = \frac{447.125}{0.1908} \approx 2343.6 \, \text{N}
  3. Substitute TT into the vertical force equation: Using Ty=Tsin(11)T_y = T \sin(11^\circ): Ry+447.125=744.8R_y + 447.125 = 744.8 Ry=744.8447.125R_y = 744.8 - 447.125 Ry297.675NR_y \approx 297.675 \, \text{N}

Final Answer:

The vertical reaction at the hinge is approximately: 297.7N\boxed{297.7 \, \text{N}}


Would you like a breakdown of the moment equation or any other part?
Here are some related questions for further understanding:

  1. How is the tension in the rope distributed in its components?
  2. What would happen if the angle of the rope were increased?
  3. How is the horizontal reaction (RxR_x) at the hinge calculated?
  4. Why does the beam's weight act at its center of mass?
  5. What are some real-world applications of static equilibrium in physics?

Tip: Always resolve forces into their components to simplify equilibrium calculations!

Ask a new question for Free

By Image

Drop file here or Click Here to upload

Math Problem Analysis

Mathematical Concepts

Static Equilibrium
Torque
Force Resolution

Formulas

Sum of vertical forces: ΣFy = 0
Sum of moments: Στ = 0
Weight: W = m * g
Torque: τ = Force * Perpendicular Distance
Trigonometric components: T_y = T * sin(θ), T_x = T * cos(θ)

Theorems

Equilibrium Conditions
Principle of Moments

Suitable Grade Level

Grades 11-12