Q U E S T I O N →
• What is Equilbrium ?
• Types of Equilbrium !!
• Examples ..
Answers
Answer:
Equilibrium is the state in which market supply and demand balance each other, and as a result prices become stable. ... The balancing effect of supply and demand results in a state of equilibrium.
There are three types of equilibrium: stable, unstable, and neutral. ... 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 to the direction of the displacement.
Answer:
LEARNING OBJECTIVES
By the end of this section, you will be able to:
State the types of equilibrium.
Describe stable and unstable equilibriums.
Describe neutral equilibrium.
It is one thing to have a system in equilibrium; it is quite another for it to be stable. The toy doll perched on the man’s hand in Figure 1, for example, is not in stable equilibrium. There are three types of equilibrium: stable, unstable, and neutral. Figures throughout this module illustrate various examples.
Figure 1 presents a balanced system, such as the toy doll on the man’s hand, which has its center of gravity (cg) directly over the pivot, so that the torque of the total weight is zero. This is equivalent to having the torques of the individual parts balanced about the pivot point, in this case the hand. The cgs of the arms, legs, head, and torso are labeled with smaller type.
In the figure a man is shown balancing a child on his hand. The child is enjoying the activity.
Figure 1. A man balances a toy doll on one hand.
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 to the direction of the displacement. For example, a marble at the bottom of a bowl will experience a restoring force when displaced from its equilibrium position. This force moves it back toward the equilibrium position. Most systems are in stable equilibrium, especially for small displacements. For another example of stable equilibrium, see the pencil in Figure 2.
A pencil is balanced vertically on its flat end. The weight W of the pencil is acting at its center of gravity downward. The normal reaction N of the surface is shown as an arrow upward. A free body diagram is shown at right of the pencil. The midpoint of the flat base of the pencil is marked as pivot point.
Figure 2. 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.
A system is in unstable equilibrium if, when displaced, it experiences a net force or torque in the same direction as the displacement from equilibrium. A system in unstable equilibrium accelerates away from its equilibrium position if displaced even slightly. An obvious example is a ball resting on top of a hill. Once displaced, it accelerates away from the crest. See the next several figures for examples of unstable equilibrium.
A pencil is tilted slightly toward left. The left end point of its flat surface is marked as the pivot point. The weight W of the pencil is acting at the center of gravity of the pencil. The normal reaction N of the pencil is acting upward at the pivot point. The line of action of the normal reaction is toward left of the line of action of the weight of the pencil.
Figure 3. 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.
A pencil is tilted toward left so that the line of action of its weight is toward left of the pivot point which is the left end of the flat end of the pencil.
Figure 4. If the pencil is displaced too far, the torque caused by its weight changes direction to counterclockwise and causes the displacement to increase.
A vertical pencil balanced at its sharp end is shown. The weight of the pencil is acting at its center of gravity and is in the line with the normal reaction N at the pivot point of the pencil.
Figure 5. This figure shows unstable equilibrium, although both conditions for equilibrium are satisfied.
A vertical pencil tilted toward left is shown. The sharp end of the pencil is down and labeled as pivot point. The weight of the pencil is acting at its center of gravity and the line of action of the weight is toward left of the pivot point.
Figure 6. If the pencil is displaced even slightly, a torque is created by its weight that is in the same direction as the displacement, causing the displacement to increase.
A system is in neutral equilibrium if its equilibrium is independent of displacements from its original position. A marble on a flat horizontal surface is an example. Combinations of these situations are possible. For example, a marble on a saddle is stable for displacements toward the front or back of the saddle and unstable for displacements to the side. Figure 6 shows another example of neutral equilibrium.