CENTER OF GRAVITY AND EQUILIBRIUM
If we look at giant structures like tall buildings, long bridges
and large dams, we observe that they are strong and stable. Engineers and
architects carefully planned these structure to make it rigid, strong and in
equilibrium so that it will not collapse especially during earthquake. Objects wherein all parts remain at
constant or fixed distances from every other parts as the object rotates are
called rigid bodies. Rigid bodies do not bend or stretch when forces act on
them. The concept of rigid bodies is an idealized model because in a natural
world, somehow materials deformed.
EQUILIBRIUM
Consider a book
that lies above the table. What are the forces acting on the book? It is just
the weight? If the only force acting on the book is the weight, the book will
be on free fall. There could be another force that acts on the book resting on
the table. There is a support force from the table and you call it the normal
force.
As shown in the
figure, the table exerts a force upward equal to the weight of the book. The
book is at rest and the net force is equal to zero. Therefore we could say that
the book is in the state of equilibrium.
CENTER OF GRAVITY
Let us recall the definition of weight. We know that weight is
the force in which the object is pulled by the earth. In the study of
equilibrium, we should know where the force acts. In chemistry, you learned
that matter is made up of tiny particles. Each of these particles has weight,
Each particle is acted by the force of gravity. The sum of the weights of all
particles that compose the matter maybe considered as concentrated in one
point. This point is called the center of gravity.
STATES OF EQUILIBRIUM
Any object at
rest can be classified in their state of equilibrium. Being stable, unstable or
neutral. The equilibrium condition is affected by the location of the center of
gravity in the object. When the center of gravity of an object is at the lowest
possible position, it is in stable equilibrium. When the center of gravity of
an object is at the highest possible position, it is in unstable equilibrium.
When the center of gravity is neither lowered nor raised when it is slightly
disturbed, it is neutral.
