6.5 Stability Flashcards
What happens to a body in stable equilibrium that gets displaced then released?
It returns to its equilibrium position.
Why does an object in stable equilibrium return to equilibrium when it is displaced and then released?
The centre of mass of the object is directly below the point of support when the object is at rest.
The weight of the object is considered to act at its centre of mass.
Thus the support force and the weight are directly equal and opposite to each other when the object is in equilibrium.
However, when it is displaced, at the instant of release, the line of action of the weight no longer passes through the point of support, so the weight returns the object to equilibrium.
What is unstable equilibrium?
a state of equilibrium of a body such that when the body is slightly displaced it departs further from the original position.
How is a plank balanced on a drum an example of unstable equilibrium?
Centre of mass of the plank is directly above the point of support when it is in equilibrium. The support force is exactly equal and opposite to the weight.
If the plank is displaced slightly, the centre of mass is no longer above the point of support.
The weight therefore acts to turn the plank further from the equilibrium position.
(if it is displaced slightly from equilibrium then released, the plank will roll off the drum.)
When will a tilted object finally topple over?
If an object on a flat surface is tilted more and more, the line of action of its weight ( which is through its centre of mass) passes closer and closer to the pivot.
I the object is tilted so much that the line of action of its weight bases beyond the picot, the object will topple over if allowed to.
What is the furthest a tilted object can go before toppling?
Where the line of action of the weight passes through the pivot.
What about the centre of mass of an object can make it more stable?
The lower the centre of mass of an object, the more stable it is
