Parallel Forces and Multiple Supports

Try these questions

5 questions from this lesson’s quiz. Start the lesson to answer them and see the right answers.

1. 1. Which pair of conditions must be satisfied for a beam resting on two supports to be in complete mechanical equilibrium?

   • A. Total upward force equals total downward force, and total clockwise moment equals total anticlockwise moment
   • B. Total upward force is greater than total downward force, and all moments are zero
   • C. The two supports carry equal forces, and the beam's weight is neglected
   • D. The centre of gravity is at the base, and the supports are at the ends

2. 2. A light horizontal beam 6 m long rests on supports at its ends, P and Q. A load of 900 N is placed 2 m from support P. Find the upward reaction force at support Q.

   Type your answer (in N) in the lesson.

3. 3. A uniform scaffold plank 5 m long weighs 300 N. It rests on supports at its ends, P and Q. A builder weighing 500 N stands 1 m from support P. Find the upward reaction force at support P.

   Type your answer (in N) in the lesson.

4. 4. When finding the reactions at two supports, why do we take moments about one of the supports?

   • A. Because the support's force has zero distance from the pivot, so its moment is zero and that unknown is eliminated
   • B. Because the support does not exert any force on the beam
   • C. Because moments can only be taken about a support and never about any other point
   • D. Because it makes the total upward force equal to zero

5. 5. What name is given to the upward contact force that a support such as a bridge pier exerts on a beam to oppose the downward loads?

   Type your answer in the lesson.

More in Moments and Equilibrium

• ▸The Principle of Moments
• ▸Centre of Gravity of Regular and Irregular Laminae
• ▸States of Equilibrium
• ▸Factors Affecting Stability and Structural Design
• ▸Torque, Couples and Resolution of Forces
• ▸Practical Applications and System Consolidation
• ▸Forms of Energy & Conservation
• ▸Concept and Measurement of Work

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