Do you know what force is? Why one object is moved when it is pulled or pushed. This is the reason of force. This is the amount of pushed or pulled an object which results the interaction of one object to other object. Both the objects feel force on each other but that is not for a long time. This exists only at the time of interaction.
The main two categories of forces are contact forces and distance forces. The first type of contact force is existed on the interaction between two objects or when they comes in physical contact; for example, frictional, tensional, normal, air resistance and some applied forces comes in this category. But the second type distant forces are existed when interacting objects are not come in physical contact; for example, the force of gravitation which is the force between earth and us or the force between the sun and planets which are at large spatial separation. Electric forces and magnetic forces are also distant forces. The other two important categories are balanced and unbalanced force. Here we are discussed about them.
Force can be broadly divided into 2 categories:1. Balanced force
2. Unbalanced force
is when two equal and opposite forces are applied on a body in two exactly opposite directions. We can say that when something is not moving then balanced forces are acting on that body. When equal and opposite forces act on a body, and the body does not move then it (body) is said to be in equilibrium or we can also state as balanced forces acting on an object.
NEWTONS LAW OF MOTION:
According to this law of motion, an object at rest and an object in motion remain in their respective state (rest and motion in the same direction with the same speed) unless and until acted upon by an Unbalanced Force.
These forces are equal and opposite to each other, acting in opposite direction, and hence are called Balanced forces
. Due to this the book follows Newton’s law of motion and hence continues to be in the state of rest. Here the book is said to be in a state of equilibrium
. There is no unbalanced force acting on it.
Now let us Consider the unbalanced force
acting on the body. Now, if we pull the book in the right direction by using our hands then the forces would be represented as:
Let us take an example of a Book lying on the table. In this case there are two kind of forces acting upon the book:
- The gravitational pull of earth (in downward direction)
- The normal reaction of the book (in upward direction)
These forces are equal and opposite to each other, acting in opposite
direction and hence are called Balanced Forces. Due to this the book
follows Newton’s law of motion and hence continues to be in the state of
Here the book is said to be in a state of equilibrium. There is no unbalanced force acting on it.
Unbalanced Force Acting on an Object
Consider the same book lying on the table and if we pull the book in the right direction by using our hand then the forces would be represented as:
In the above figure we can see that the Force F1 balances the Force F2 but there is another Force F3 ( PULL) which is unbalanced. As a result the book moves in the direction of pull thus satisfying the Newton's law of motion.
Example 1: AERODYNAMICS
Here lift balances weight and thrust balances drag.
Example 2: STANDING ON THE GROUND
- Weight: pulls in the downward direction.
- Thrust: in left direction.
- Drag: in right direction.
When we stand on the ground our weight is balanced by the reaction from the ground, hence balanced forces. The ground basically pushes us. Without this reaction force we would have sunk in the ground.
Figure: Man Standing Still
Example 3: Tug of War
Balanced condition, in a tug of war, when the rope is still is also an example of balanced force. Let’s assume you are playing tug of war with a team. Your team starts with all its strength and the team on the other side is also pulling with the same force but in an opposite direction. Due to this the flag in the middle of the rope does not move. This is because force from both the sides cancels out each other, the net force is zero and we get a condition of balanced force.
Figure: Tug of war
The magnitude of the overall force acting upon the object is called the overall force. The overall forces are determined by drawing Free Body Diagram of the object under inspection.Condition for balanced force:
The resultant force acting upon the body should be equal to zero. There are two terms which we must be very much familiar with while studying balanced forces:1
. Gravity :
Gravity is the force which is exerted by earth on bodies and objects. It tends to pull the objects and bodies towards the earth.
Example: To hold up the bag of vegetables the force of pull exerted on it must balance the force of gravitation exerted by the earth surface. 2. Friction :
Friction is the force which opposes the motion of two bodies in contact with each other. In other words friction acts between two bodies in contact.
Example: Imagine pushing a heavy bucket full of water but it's not moving. This is because the force of friction acting in the opposite direction of the motion of the bucket balances out the force of push exerted by you.3. Free body diagram :
The diagrammatic representation of all the forces acting upon the object in action is called the free body representation of the object. Free body diagram are useful for determining the net force or the resultant force acting upon the body as well as determining easily the nature of forces acting upon the body viz. balanced force or unbalanced force.
Imagine a force of 20 N exerted on the box but it does not move. Hence the free body representation of the box would be:
Forces N: Normal in the upward direction
Weight W: In the downward direction
Friction to the right
20 N to the left