Moments (Edexcel A Level Physics): Flashcards
Exam code: 9PH0
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Define moment.
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Cards in this collection (13)
Define moment.
The turning effect of a force about a pivot.
State the equation for the moment of a force.
Moment = force × perpendicular distance from the pivot
Measured in newton metres (N m)
The moment of a force is the force multiplied by the .......... distance from the pivot.
The moment of a force is the force multiplied by the perpendicular distance from the pivot.
What is the SI unit of the moment of a force?
The newton metre (N m)
Why is a door handle placed as far as possible from the hinge?
To maximise the perpendicular distance from the pivot (the hinge)
This gives a greater moment for the same force, making the door easier to open.
True or False?
The distance used to calculate a moment is the distance from the pivot measured along the direction of the force.
False.
You must use the perpendicular distance from the pivot to the line of action of the force, not the distance measured along the force.
Define centre of gravity.
The single point through which all the weight of an object can be considered to act.
Also called the centre of mass.
Where is the centre of gravity of a symmetrical object of uniform density?
At its point of symmetry.
For a uniform regular solid, this is at its centre.
An object is stable when its centre of gravity lies above its ...........
An object is stable when its centre of gravity lies above its base.
How does the width of an object's base affect its stability?
A wider base gives a lower centre of gravity and greater stability
A narrower base gives a higher centre of gravity, so the object topples more easily
True or False?
The centre of gravity of every object is located at its exact geometric centre.
False.
This is only true for symmetrical objects of uniform density. For irregular or non-uniform objects the centre of gravity lies elsewhere.
State the principle of moments.
For a system in equilibrium, the sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point.
For a system in equilibrium, the sum of the clockwise moments about a point equals the sum of the .......... moments about the same point.
For a system in equilibrium, the sum of the clockwise moments about a point equals the sum of the anticlockwise moments about the same point.
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