Moments & Equilibrium — A/L Physics

How do I practise Moments & Equilibrium?

1 question with a worked solution

1. A uniform horizontal beam AB of length 4.0 m and weight 200 N is pivoted at end A and supported horizontally by a vertical cable attached at end B. A 600 N weight is placed on the beam at a distance of 1.0 m from A. What is the tension in the vertical supporting cable?
   1. A) 250 N
   2. B) 300 N
   3. C) 200 N
   4. D) 400 N
   Check my answer

   Correct answer: A) 250 N

   Taking moments about pivot A in static equilibrium: Sum of clockwise moments = Sum of anticlockwise moments. Clockwise moments: Weight of beam at center of gravity (2.0 m): 200 N × 2.0 m = 400 N m. Added weight at 1.0 m: 600 N × 1.0 m = 600 N m. Total clockwise moment = 1000 N m. Anticlockwise moment = T × 4.0 m. Hence, 4.0 T = 1000 => T = 250 N.

   Show worked solution

   Step 1: Take moments about pivot A: Στ_A = 0. Step 2: (200 N × 2.0 m) + (600 N × 1.0 m) - (T × 4.0 m) = 0. Step 3: 400 + 600 = 4.0 T => 1000 = 4.0 T => T = 250 N. Answer: 250 N.
   Modelled on: the A/L Physics examination pattern

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Where does Moments & Equilibrium fit in the syllabus?

Unit 2.3 · Year 1 · Term 1