When a system is said to be in equilibrium this means it is in balance and is either moving at constant velocity motion or is at rest.
Situations that must exist for a system to be at equilibrium:
- The resultant force in any direction must be zero.
- The total moments of the system must be zero. Meaning:
Clockwise Moments = Anti- Clockwise Moments
How to calculate equilibrium?
Example 1
If the system below is in equilibrium find the unknown force “F”.
System in equilibrium |
In the question they stated that the system is in equilibrium, therefore you can go ahead and use the equation:
Clockwise Moments = Anti-Clockwise Moments
But remember that formula for moments is:
Force × Perpendicular distance from pivot
Therefore:
Clockwise Force × Perpendicular distance = Anti-clockwise Force × Perpendicular Distance
Identify the forces in the system that are moving clockwise and anti-clockwise with their respective perpendicular distances, and then substitute those values in the above equation:
Clockwise Moments = Anti-Clockwise Moments
Clockwise Force × Perpendicular distance = Anti-clockwise Force × Perpendicular Distance
F × 8m = 120N × 6m
Step 3
After placing the values into the formula all that is left to do is transpose the formula to make “F” the subject then solve for “F”. The overall calculation would then be:
Calculating Equilibrium |
1 Response to Calculating Equilibrium in a System of Force
Hi! With this post you reminded me of my physics teacher. He was really a great guy! I learnt a lot about physics with him.
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