BRAINCAKEMoments Question 2
Question: a uniform plank of length 4.0 m and weight 200 N rests horizontally on two supports, A at the left end and B at the right end. A person of weight 600 N stands 1.0 m from A. Calculate the upward forces RA and RB from the supports.
Step 1: find the centre of gravity. The plank is uniform, so its 200 N weight acts at its midpoint, 2.0 m from A.
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Key terms in this lesson
- moment
- The turning effect of a force, equal to the force multiplied by the perpendicular distance from its line of action to the pivot.
- equilibrium
- A state in which the resultant force and resultant moment on an object are both zero, so it has no tendency to accelerate or turn.
- centre of gravity
- The single point through which the whole weight of an object appears to act.
More in Motion
- Free-Body Force Diagrams
- The Moment of a Force
- Centre of Gravity
- Moments Question 1
- Newton's First Law of Motion
- Newton's Second Law of Motion
- Newton's Third Law of Motion
- Constant Acceleration
All 31 lessons in Motion · All Edexcel AS-level Physics topics