6.5 Stability Flashcards
What does it mean if a body is in stable equilibrium?
» If it is displace then realised, it returns to its equilibrium positon
Why does an object in stable equilibrium return to equilibrium when it is displaced and then released?
» As 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 in equillibrium
What happens in stable equilibrium at the instant of release?
» The line of action of the weight no longer pass through the point of support, so weight returns the object equilibrium
What does it mean if a body is in an unstable equilibrium?
» If it displaced slightly from equilibrium and then released, the object will not return to its equilibrium position?
Why does a body in unstable equilibrium not return to its resting position?
» Centre of mass of the object is directly above the point of support when it’s in equilibrium
» Support force is exactly equal and opposite to the weight
» If the plank is displaced slightly, the center of mass is no longer above the point of support
» Weight, therefore, acts to turn the object further from the equilibrium position
What is tilting?
» Where an object at rest on a surface is acted on by a force that raised it up on one side
How can you make a bookcase tilt?
» The force must turn it clockwise about point
» The weight of the bookcase provides an anticlockwise moment about P
» For tilting to occur in the book case , clockwise > weight moment
How will a tilted object topple over?
» If it is tilted too far
» The line of action of its weight - which is through its centre of mass passer closer to the pivot
» If the line of action passed beyond the pivot, it wall fall over
When will an object topple over on a slope?
» If the line of action of the weight lies outside the wheelbase of the vehicle
