What Is Force?
An object continues to do what it is doing unless some external unbalanced force acts on it. So, forces play an important role in physics because It is the force only which allows motion of an object. Balanced forces do not cause things to move. They do not produce any acceleration. Unbalanced forces can change the state of motion of an object.
What Is Force?
Force can be defined as push or pull on an object which provides motion to an object. Every object on the Earth experiences various forces. Force is a vector quantity. So, it has a magnitude and a direction. Forces can never be seen, but its effects can be observed in the form of motion of an object. Pushing of chair, pulling of door are all the results of applied force. Force that we apply on an object can change the speed, direction, shape and size of an object. Forces can be balanced or unbalanced.
Balanced Forces And Unbalanced Forces
When an object is in equilibrium, that means, it is not moving with a changing speed or velocity, then net force acts on it is known as balanced force. When the number of forces acting on an object are such that their resultant force is zero, then the forces are said to be balanced. If the forces are balanced, then there can be two cases. An object may be at rest or an object will be in motion at a non zero constant velocity in a certain direction. In the first case, the object will continue to remain at rest. In the second case, the object will continue to stay in motion at the same velocity and in the same direction.
Balanced Force
The image shown above is a real life example of balanced forces. This person is pushing against the wall and the wall is not moving. That means, the wall is actually pushing back on this person with an equal force but in the opposite direction.
When an object is not in equilibrium, that means it is moving with changing speed or velocity, then the net force acting on that object is known as unbalanced forces. When the number of forces acting on the object are such that their resultant force is not equal to zero, then the forces are said to be unbalanced.
Unbalanced Force
The image shown above is an example of unbalanced force. When we kick the football, the football starts moving in the direction of a larger force acting on it. Hence, when we kick a football and it moves from one place to another, we can say that unbalanced forces are acting upon it. That means, the net force is not equal to zero. Unbalanced force is responsible for this kind of motion.
Effects Of Balanced And Unbalanced Forces
Balanced forces will cause no change in the speed of an object. When two unbalanced forces act in opposite directions, their combined force will be equal to the difference between the two forces. If the net force applied on an object is not equal to zero, that means, the force on one side is greater than the other, then the forces are said to be unbalanced forces.
Characteristics Of Balanced And Unbalanced Forces
Here are some interesting characteristics about balanced forces:
If a number of balanced forces are acting on a stationary object, then that object doesn’t change its state of rest. So, we can conclude that if a number of balanced forces are acting on an object which is at rest, then these forces can not result in the motion of the object which is stationary.
If a number of balanced forces act on an object which is in uniform motion, then the object continues to be in its state of uniform motion. That means these balanced forces can not change the state of uniform motion of an object.
Balanced forces neither produce motion in a stationary object nor can they stop a moving object.
Balanced forces can change the shape of an object even though they can not set a stationary object to motion or they can not set the object which is moving to rest.
Here, are some characteristics of unbalanced forces:
Unbalanced forces can change the state of an object from rest or uniform motion.
They can move a stationary object whenever the object is at rest.
They can stop a moving object.
They can change the speed of an object as well as the direction of the moving object.
Solved Examples
1. What force would be needed to produce
Ans: Given: acceleration
mass
Here, we will use the relation
Therefore,
So, the required force is
2. Calculate the force to impart to a bus a velocity of
Ans: Given: Here, the bus is starting from a rest position. So, initial speed of the bus is
Final speed of the bus
Mass of the bus
Time taken
We will use the relation
Now, we will use the formula
So,
So, the required force is
Interesting Facts
If we apply a balanced force on any object, then that object would not change its state of motion or rest.
Newton’s second law explains to us that unbalanced force causes acceleration.
Sir Issac Newton developed laws of motion.
Conclusion
So, we can conclude that balanced forces do not allow the moving object to change its direction or its speed. If balanced force acts on an object at rest, then we can say that the object can not move. If unbalanced force acts on an object at rest, then the object will start moving in the direction of greater force.
FAQs on Balanced And Unbalanced Forces
1. What is the main difference between balanced and unbalanced forces?
The primary difference lies in their effect on an object's motion. Balanced forces are equal in size and opposite in direction, resulting in a net force of zero. They do not cause a change in the object's state of motion; it either remains at rest or continues to move at a constant velocity. In contrast, unbalanced forces are not equal and opposite, resulting in a non-zero net force that causes a change in the object's motion, such as starting, stopping, or changing direction.
2. Can you provide some real-world examples of balanced and unbalanced forces?
Certainly. Here are some common examples of both types of forces in action:
- Examples of Balanced Forces:
- A book resting on a table (the downward force of gravity is balanced by the upward support force from the table).
- A game of tug-of-war where neither team is moving.
- A car moving at a constant speed on a straight highway (the engine's forward thrust is balanced by air resistance and friction).
- Examples of Unbalanced Forces:
- Kicking a football (the force of the kick is greater than air resistance, causing the ball to accelerate).
- An apple falling from a tree (the force of gravity is an unbalanced force pulling it down).
- Pushing a swing to make it go higher (the applied push is an unbalanced force that changes the swing's motion).
3. If balanced forces are acting on an object, does it mean the object must be at rest?
No, not necessarily. This is a common misconception. While an object at rest will remain at rest under balanced forces, an object already in uniform motion (moving at a constant speed in a straight line) will also continue in that state. For example, a satellite orbiting Earth at a constant speed experiences balanced forces. The key is that balanced forces result in zero acceleration, meaning no change in velocity, whether that velocity is zero or a constant value.
4. What effect can balanced forces have on an object if they cannot change its state of motion?
While balanced forces cannot cause an object to accelerate (i.e., change its state of rest or uniform motion), they can change the shape or size of a non-rigid object. For instance, when you squeeze a sponge, you apply balanced forces with your hands. The sponge doesn't fly away, but it compresses and changes its shape. Similarly, stretching a rubber band involves applying balanced forces in opposite directions, causing it to elongate.
5. How are unbalanced forces related to Newton's First Law of Motion?
Newton's First Law of Motion, the law of inertia, states that an object will remain at rest or in uniform motion unless acted upon by an external unbalanced force. This law fundamentally defines the role of unbalanced forces. It is the presence of an unbalanced force that overcomes an object's inertia and causes acceleration, which is a change in velocity. In essence, unbalanced forces are the agents of change in motion.
6. Why is an unbalanced force necessary to make a moving object change direction?
Changing direction is a form of acceleration, even if the object's speed does not change. This is because velocity is a vector, defined by both speed and direction. According to Newton's laws, any acceleration requires a net unbalanced force. To alter an object's path, a force must be applied that is not aligned with its current direction of motion. A classic example is a planet orbiting the Sun; the Sun's gravity provides a constant unbalanced force that continually changes the planet's direction, keeping it in orbit.
7. What is 'net force' and how does it determine if forces are balanced or unbalanced?
The net force is the vector sum of all the individual forces acting on an object. It represents the overall or resultant force. This concept is crucial for determining the type of forces, as per the CBSE/NCERT curriculum for the 2025-26 session.
- If the net force on an object is zero, the forces are considered balanced. They cancel each other out, leading to no change in motion.
- If the net force is greater than zero, the forces are unbalanced. This resultant force causes the object to accelerate in the direction of the net force.
