State the principle of moments .

For a system in equilibrium, the sum of clockwise moments about a point equals the sum of anticlockwise moments about the same point.

For a uniform beam, where does its weight act when applying the principle of moments?

At its centre of gravity , which for a uniform beam is its midpoint .

True or False? The principle of moments applies to any system, whether or not it is in equilibrium.

False. The principle of moments only applies when a system is in equilibrium , i.e. when the sum of clockwise moments equals the sum of anticlockwise moments.

A system is in equilibrium when there is no resultant force and no resultant torque acting on it.

According to Newton's First Law, how does an object in equilibrium behave?

It remains at rest or moves at constant velocity , and does not rotate .

How are coplanar forces in equilibrium represented graphically?

As a closed vector triangle — the vectors, joined tip to tail, form a closed path.

Name the four common forces most often considered in coplanar equilibrium problems.

Weight Normal reaction force Tension Friction

To form a vector triangle for forces in equilibrium, draw a free-body force diagram, then rearrange the force arrows .......... while maintaining their length and direction.

To form a vector triangle for forces in equilibrium, draw a free-body force diagram, then rearrange the force arrows tip to tail while maintaining their length and direction.

True or False? An object is only in equilibrium if it is at rest.

False. An object in equilibrium may also be moving at constant velocity — equilibrium requires zero resultant force and zero resultant torque, not necessarily being stationary.

A LevelPhysicsCambridge (CIE)Flashcards4. Forces, Density & PressureEquilibrium of Forces

Equilibrium of Forces (Cambridge (CIE) A Level Physics): Flashcards

Exam code: 9702

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FrontPrinciple of Moments
State the principle of moments.

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Cards in this collection (10)

State the principle of moments.
For a system in equilibrium, the sum of clockwise moments about a point equals the sum of anticlockwise moments about the same point.
When multiple forces produce moments on the same side of a pivot, how are they combined in the principle of moments equation?
Their moments are summed together, e.g. if F₁ and F₃ both produce anticlockwise moments and F₂ produces the clockwise moment: $F_{2} d_{2} = (F_{1} d_{1}) + (F_{3} d_{3})$
For a uniform beam, where does its weight act when applying the principle of moments?
At its centre of gravity, which for a uniform beam is its midpoint.
True or False?
The principle of moments applies to any system, whether or not it is in equilibrium.
False.
The principle of moments only applies when a system is in equilibrium, i.e. when the sum of clockwise moments equals the sum of anticlockwise moments.
Define equilibrium.
A system is in equilibrium when there is no resultant force and no resultant torque acting on it.
According to Newton's First Law, how does an object in equilibrium behave?
It remains at rest or moves at constant velocity, and does not rotate.
How are coplanar forces in equilibrium represented graphically?
As a closed vector triangle — the vectors, joined tip to tail, form a closed path.
Name the four common forces most often considered in coplanar equilibrium problems.
- Weight
- Normal reaction force
- Tension
- Friction
To form a vector triangle for forces in equilibrium, draw a free-body force diagram, then rearrange the force arrows .......... while maintaining their length and direction.
To form a vector triangle for forces in equilibrium, draw a free-body force diagram, then rearrange the force arrows tip to tail while maintaining their length and direction.
True or False?
An object is only in equilibrium if it is at rest.
False.
An object in equilibrium may also be moving at constant velocity — equilibrium requires zero resultant force and zero resultant torque, not necessarily being stationary.

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