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Presentation 1.pptx
PHYSICAL EQUILIBRIUM
AIMS OF PRESENTASTION
DEFIINE EQUILIBRUIM
EXPLAIN EQUILIBRIUM TYPES
GIVE EXAMPLES OF EQUILIBRIUM
SHOW THE CONDITIONS AND FORCES RESPONSIBLE FOR EQUILIBRIUM
EQUILIBRIUM TYPES
STABLE EQULIUBRIUM
UNSTABLE EQUILIBRIUM
NEUTRAL EQULIBRIUM
STABLE EQUILIBRIUM
When the center of gravity of a body lies below the point of suspension or support, the body is said to be in a state of stable equilibrium .
Examples of Equilibrium
STABLE EQUILIBRIUM
A Book lying on a horizontal surface is an example of stable equilibrium . If the book is lifted on one edge and then allowed to fall, it will come back to its original position. Other examples of stable equilibrium are bodies lying on a floor such as a chair
Reason for stability: the book is lifted its center of gravity is raised. The line of action of the weight passes through the base of the book . A torque due to weight of the book brings it back to the original position
Unstable equiliubrium
When the center of gravity of a body lies above the point of suspension or support, the body is said to be in unstable equilibrium
UNSTABLE EQUILIBRIUM EXAMPLE
Pencil standing on its point or a stick in a vertical standing position.
Reason: when the rod is standing vertically is slightly disturbed from its position it will not come back to its original position. This type of equilibrium is called unstable equilibrium, other example of unstable equilibrium are vertically standing cylinder or funnel.
Reason for instability . When rod is slightly disturbed its center of gravity is lowered. The line of action of its weight lies outside the base of the rod. The torque due to the weight of the the rod topples it down.
STABLE EQULIBRIUM EXAMPLE
In figure . This pencil is in the condition of equilibrium. The net force on the pencil is zero and the total torque about any pivot is zero.
EQUILIBRUIM EXAMPLE
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If the pencil is displaced slightly to the side (counterclockwise), it is no longer in equilibrium. Its weight produces a clockwise torque that returns the pencil to its equilibrium position.
UNSTABLE EQULIBRIUM
If the pencil is displaced too far, the torque caused by its weight changes direction to counterclockwise and causes the displacement to increase.
Neutral Equilibrium
The center of gravity of a body lies at the point of suspension or support, the body is said to be in neutral equilibrium . Example , a rolling ball.
If a ball is pushed slightly to roll, it will neither come back to its original position nor will it roll forward, rather it will remain at rest . This type of equilibrium is called neutral equilibrium .
Reason for neutral. If a ball is rolled, its center of gravity is neither raised or lowered. This means the center of gravity is at the same height as before.
Neutral Equilibrium
Figure . (a) here we see neutral equilibrium. The cg of a sphere on a flat surface lies directly above the point of support, independent of the position on the surface. The sphere is therefore in equilibrium in any location, and if displaced, it will remain still. (b) Because it has a circular cross section, the pencil is in neutral equilibrium for displacements perpendicular to its length.
Homework
HOME EXPERIMENT
Stand straight with your heels, back, and head against a wall. Bend forward from your waist, keeping your heels and bottom against the wall, to touch your toes. Can you do this without toppling over? Explain why and what you need to do to be able to touch your toes without losing your balance. Is it easier for a woman to do this?
PRESENTATION SUMMARY
A system is said to be in stable equilibrium if, when displaced from equilibrium, it experiences a net force or torque in a direction opposite the direction of the displacement.
A system is in unstable equilibrium if, when displaced from equilibrium, it experiences a net force or torque in the same direction as the displacement from equilibrium.
A system is in neutral equilibrium if its equilibrium is independent of displacements from its original position.
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