AS Physics Unit 1.3 Principle Of Moments Flashcards
What is the definition of a moment?
The moment of a force about a point is defined as the product of the force and the perpendicular distance from the point to the line-of-action of the force.
What is the equation for a moment?
M = F x d or Moment = Force x perpendicular distance from the point to the force.
What are the units from force and distance?
Newtons (N) and Metres (m).
What are the units for moments?
Newton-metres (Nm)
What are the two directions a moment can be?
The direction of a moment can be clockwise or anti-clockwise.
What is the definition of a couple?
A couple is two forces that act in opposite directions, not along the same line and which cause a rotations.
What moment does a couple produce?
It produces and unbalanced moment.
What is the equation a couple?
M = F x d or Moment of Couple = One Force x Perpendicular Separation of the Forces.
What is the definition of the centre of gravity?
The centre of gravity of an object is the point at which we can take its weight to act.
What is the definition of the centre of mass?
The centre of mass of an object is the point at which we take its mass to be concentrated.
How would an object move if the resultant force acts through the centre of mass?
It would move in a straight line without causing it to rotate.
Where is the centre of gravity of a uniform beam?
At its mid-point.
What is the definition of the principle of moments?
The principle of moments states that when an object is in rotational equilibrium, the sum of the clockwise moments about any point is equal to the sum of the anti-clockwise moments about the same point.
What tow conditions must be met for equilibrium to be the state of a system?
There must be no resultant force in any direction (e.g. must balance) and the sum of the clockwise moments about any point equals the sum of the anti-clockwise moments about the same point.
