Lab Overview
Two painters, Sue and Jack, are working on a 10-meter platform suspended from the side of a building by two cables. Your task is to analyze the static equilibrium of this system using torque equations (Στ = 0) to find the tension in each cable under two different conditions.
In Case 1, the painters are at fixed positions and you calculate both cable tensions. In Case 2, you find how far Sue can walk toward Jack before the platform begins to tip (Cable 2 tension goes to zero).
Platform = 184 N
Sue = 130 N
Jack = 220 N
Platform length = 10 m
Cable 1 at x = 0 m (left)
Cable 2 at x = 10 m (right)
Q
Team Questions
Question 1. When a force is applied to a pipe wrench, the torque produced on the pipe can be positive or negative depending on the direction of rotation it tends to cause. Using the convention that counterclockwise (CCW) torques are positive and clockwise (CW) torques are negative, answer: when the force applied to the wrench tends to rotate the pipe clockwise, the torque is:
1
Interactive Platform Simulation
Case 1 — Fixed Positions
Sue at 2 m, Jack at 7 m from left end
Case 2 — Find Tipping Point
⚠ Platform tipping! Cable 2 tension has dropped to zero. Sue has reached the critical tipping point.
Jack stays at 7 m. Slide Sue until T₂ = 0
2
Calculations & Analysis
Free Body Diagram Setup: Pivot at Cable 1 attachment point (x = 0). Torques: Platform weight acts at x = 5 m (center). Sue at x = 2 m. Jack at x = 7 m. T₁ acts upward at x = 0 (zero moment arm from pivot). T₂ acts upward at x = 10 m. CW torques are negative.
Step-by-Step Torque Solution — Case 1
Set positions using the Case 1 sliders above, then click "Set Case 1 Positions"
Tipping Analysis: When the platform is about to tip over Cable 1, Cable 2 becomes slack — T₂ = 0. The pivot is still at Cable 1 (x = 0). With T₂ = 0, the only unknowns are T₁ and Sue's critical position. Use ΣF = 0 and Στ = 0 with T₂ = 0.
Step-by-Step Tipping Point Solution — Case 2
Use the Case 2 slider or click "Auto-Find Tipping Point" to calculate.
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Results Table
Data Table — Calculated vs. Measured Values
| Parameter | Calculated (from equations) | Measured (from simulation model) | % Difference |
|---|---|---|---|
| Case 1 — Cable 1 (T₁) | — | — | |
| Case 1 — Cable 2 (T₂) | — | — | |
| Case 2 — Cable 1 (T₁) | — | — | |
| Case 2 — Cable 2 (T₂) | — | — | |
| Case 2 — Sue's Critical Position | — | — |
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Lab Report
Written Analysis — Answer all sections completely