3.4.1.2 Moments Flashcards
What is a moment?
A moment is the turning effect of a force.
What does the moment of a force depend on?
The size of the force.
How far the force is applied from the turning point.
What is the equation for moment?
Moment of a force = Force x Perpendicular distance from the pivot point.
What is the unit for the moment of a force?
Newton-metres.
What does the principle of moments state?
The principle of moments states that for a body in equilibrium, the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about the same point.
What will happen is the moments of an object are not balanced?
The object will turn.
What is a couple?
A couple is a pair of coplanar forces. The forces are of equal size, and act parallel to each other, but in opposite directions.
Will a couple cause a resultant force?
A couple doesn’t cause any resultant linear force, but does produce a turning effect.
What is the equation for the moment of a couple?
Moment of a couple = size of one of the force x perpendicular distance between the line of actions of both forces.
What is the mass of a body?
The mass of an object is the amount of matter in it. It is measured in kg.
What does mass resist?
The mass of a body makes it resist changes in motion.
What is the relationship between mass and an objects resistance to motion?
The greater an objects mass, the greater its resistance to change in velocity (its inertia).
What is the equation for weight?
Weight = mass x gravitational field strength. W = m x g
What is the centre of mass of an object?
The centre of mass of an object is the single point that you can consider its whole weight to act through. The object will always balance around this point.
Describe a toppling object.
An object will topple over if the line of action of its weight falls outside its base area. There will be a net moment about a pivot, which will cause it to rotate and fall over. A resultant moment produces a turning force.
