Have you ever been a part of the tug of war? What happens is all players are divided into two teams. Each team is asked to stand on either side of a rope. A ribbon is tied in the middle of the rope, and the team that can pull the rope towards its side and get the ribbon wins.

Once players of both teams take their positions, the game starts. The ribbon stays in the middle as long as both sides apply the same force to the rope. To win the game, a team will have to apply a force greater than the force applied by the opposite team and pull the rope strongly towards its side. Let us read further to understand how these equal and unequal forces work and the balance or imbalance created by the application of forces.

What is Force?

Forces are everywhere around us. From lifting a small pen to kicking a ball, everything involves a force. Forces are needed to move, shift, rotate, turn, stop, catch, drag or drop. A force can be defined as a push or a pull that can cause a stationary object to move, a moving object to slow down or stop or change its direction of motion. Examples of force are the friction force that helps us move or gravity, which causes all objects to fall towards the earth’s surface.

Force is a vector quantity; it has both direction and magnitude. Like any other vector quantity, Forces acting on an object can be represented by arrows. The length of the arrow represents the magnitude of the force and the head of the arrow points in the direction of the force. Thus, by using the arrows, we can determine the resultant force and the direction of the force.

The SI unit of force is newton \((\rm{N})\) and is represented by the symbol \(F\).

Mathematically, the force acting on a body can be given as \(F = m \times a\)

Here, \(F\) is the force, \(m\) is the mass, and \(a\) is the acceleration of a body.

Forces acting on an object can be balanced or unbalanced.

Types of Forces

A body can experience more than one force at a given time. In fact, there are at least two or more forces acting on any surface most of the time. For example, when we throw a ball upwards, the ball will experience the force of our hand, downwards force of gravity, the force of air resistance and friction due to air. Depending on the net force acting on a body due to the application of these forces, there are two possible categories of forces that can act on a given object. These are:

1. Balanced Forces: These forces occur when two equivalent forces work in opposite directions on a surface.
2. Unbalanced Forces: These forces occur when two forces act in opposite directions on a surface unequal in magnitude and size.

The effect of these forces on a surface is different. Let us see how each of these forces work.

What is a Balanced Force?

When forces applied to a body are equal in magnitude but in the opposite direction, the type of net force that acts on the body is termed Balanced Force. In simple words, a balanced force is a force where two equal forces act on a body in exactly reverse directions.

Under the impact of a balanced Force, a body continues to be in its position, i.e. it may be continuously moving with the same speed and in the same direction, or it may be stationary in its position. Thus, when balanced force is applied to a body, then the body doesn’t support the motion. Instead, distortion of the body can happen.

A rigid body (if we ignore deformations and rotation) on which balanced forces are acting behaves as if no forces were acting on it. Thus, when subjected to a balanced force:

1. An object at rest stays at rest.
2. An object in motion continues to move at the same speed and in the same direction. ( Here, remember that a force is not required to maintain an object in its state, a force is required when we need to change the state of motion of an object)

Examples of Balanced Force

• 1. When two wrestlers participating in arm wrestling exerts a similar force on each other but push against each other in opposite directions, there will be no winner. Thus, the net force (resultant force) is \(0\) or balanced.
• 2. In a tug of war, if the rope does not move, the two teams are exerting equal yet opposing balanced forces on the rope. Thus, the resultant force or net force on the rope is zero.

• 3. The forces on a hanging crate, i.e. the weight of the crate that pulls it down and the tension in the rope that pulls it up, are equal in size but act in opposite directions.
• 4. When the upthrust compensates for the weight of an object from the sea, it floats, and the forces acting on the object will be balanced.

• 5. The ground’s reaction force balances the weight when an object is resting on a flat surface, such as the earth. The object’s weight gets balanced by the normal force of the surface, which is true for when we are standing too.
• 6. When we push a wall, and as expected,  neither the wall moves and nor do you. It demonstrates that you and the wall are exerting a balanced force on each other.

The balanced forces acting on a body are of the same magnitude, but their direction is opposing, so the net force will be obtained by subtracting the two forces will be zero.

What is an Unbalanced Force?

When an unequal amount of force is applied to the body in the same or opposite direction, this type of force is termed Unbalanced Force. Thus, in simple terms, a force is said to be unbalanced if it consists of two forces acting in opposing directions on a body that are not equal in magnitude and size. When unbalanced force is applied to a body, there is a change in the body’s state of motion and the direction in which the magnitude of the force is greater. Thus, under the effect of an unbalanced force, a body changes its state of motion, i.e. we can observe a change in direction, or an increase in the speed or decrease in the speed of a moving object and an object at rest starts to move, or a moving object may come at a halt in the direction.

Thus, when an unbalanced force acts on a body, the following few cases are possible:

1. An object at rest starts to move in the direction of the resultant force.
2. An object in motion may come at rest under the effect of the force.
3. An object in motion can experience a change in its speed and direction of motion.

Examples of Unbalanced Force

• 1. In general, the motion of any object is a result of the application of unbalanced forces on it. If you kick a football and it moves from one place to another, it means that that the forces acting on the football are unbalanced forces.
• 2. In the tug of war, when one side pulls the rope with greater force than the opponent side, the rope will move in the direction where the strength of the force is greater.

• 3. When two people simultaneously pull on an object in the same direction, the object’s applied force results from their combined forces.
• 4. When a fruit falls from a tree, it experiences an unbalanced force proportional to its weight.
• 5. When a moving car suddenly stops, the forces acting on the car are unbalanced.

The unbalanced forces acting on an object are added if the forces acting on the object are in the same direction and subtracted if the forces acting on the object are in the opposite direction.

Problems Based on Balanced and Unbalanced Force

Question: Consider a body initially at rest. A force of \(80\;\rm{N}\) is applied to the body towards the right side, while \(240\;\rm{N}\) is applied towards the left side. Calculate the net force on the body and the direction of the net force.

Solution: Net Force \(=\) Force towards the left side \(–\) Force towards the right side
\(= 240\;\rm{N} – 80\;\rm{N}\)
\(= 160\;\rm{N}\)
Direction Of Force: Left side (As Larger Amount Of Force Is Applied On The Left Side Of The Body)

Question: What will be the net force acting on the block given below:

Solution: The forces acting on the block are on opposite sides; the net force acting on the bloc is:
\(25\;\rm{N} – 25\;\rm{N} = 0\;\rm{N}.\)
The forces acting on the block are balanced.

Summary

A force can be defined as a push or a pull that can cause a stationary object to move, a moving object to slow down or stop or change its direction of motion. Depending on the net force acting on a body due to the application of these forces, there are two possible categories of forces that can act on a given object. These are:

1. Balanced Forces: These forces occur when two equivalent forces work in opposite directions on a surface. A book kept on a table is an example of balanced forces acting on an object.
2. Unbalanced Forces: These forces occur when two forces act in opposite directions on a surface unequal in magnitude and size. A book moving on a table after a push by your hand is an example of an unbalanced force acting on a body.

FAQs on Blanced and Unbalanced Force

Q.1. What is a force?
Ans: A force can be defined as a push or a pull that may deform an object, or change the direction of an object’s motion or change the speed of a moving object, or start the motion of an object at rest or stop the motion of an object moving.

Q.2. What is a balanced force?
Ans: A force that does not cause a change in the motion of a body is known as a balanced force.

Q.3. What is an unbalanced force?
Ans: A force that causes a change in the motion of a body is known as an unbalanced force.

Q.4. What type of force acts on a ball when it is thrown towards the batsman by a bowler?
Ans: The forces acting on the ball are unbalanced.

Q.5. What is the resultant force on a body acting under the effect of balanced forces?
Ans: The resultant force on a body acting under the effect of balanced forces is always zero.

Study Work Done by Variable Force

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