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level: Moments

Questions and Answers List

level questions: Moments

Question	Answer
The moment is the force multiplied by the perpendicular distance from the line of action of the force to the point.	Moment of a Force
What is the formula to calculate the moment of a force?	Moment = Force × Perpendicular distance from the point to the line of action of the force.
A pair of coplanar forces (forces within the same plane) that are equal in magnitude but act in opposite directions.	Couple
The moment of a couple is found by multiplying one of the forces by the perpendicular distance between the lines of action of the forces.	Moment of a Couple
How do you calculate the moment of a couple?	Moment of a couple = Force × Perpendicular distance between the lines of action of the forces.
States that for an object in equilibrium, the sum of anticlockwise moments about a pivot equals the sum of clockwise moments.	Principle of Moments
What does the principle of moments state about an object in equilibrium?	The sum of anticlockwise moments equals the sum of clockwise moments for an object in equilibrium.
Given: 35 N force at 3 m from point A 50 N force at 2 m from point A Distance from A to the line of action of the force F is 3.5 m Moments are taken around A The value of F from the diagram can be found.	Moment Diagram
How can F be found in the diagram below?	By taking moments around A.
Σ Clockwise moments = Σ Anticlockwise moments: (2 x 50) + (3 x 35) = (3.5 x F) 205 = 3.5F F = 58.6 N.	Example Calculation
Why is there no anticlockwise moment affecting A?	In the example moments are taken about A, as the distance from A to A is 0, the moment caused by the 12 N force is also 0, therefore it can be ignored.
The point at which an object’s mass acts. For uniform objects, the centre of mass is located exactly at its centre.	Centre of Mass
Where is the centre of mass located in a uniform object?	The centre of mass is exactly at the centre of a uniform object.