Force: When a body tends to modify or change the state by an external cause, it is called Force. The body can also change its shape, size and direction when applied force. For example, kicking a ball, pulling and pushing the door or kneading the dough.

The concept of force comes from Isaac Newton’s Three Laws of Motion. Force is defined as the “product of mass and acceleration of a body” according to Newton’s second law. In this article, let us learn more about the Force formula, with some practice questions.

What is Force?

Anything that causes an object to undergo unnatural motion is known as Force. We require force to perform any activity. Usually, we start our day by moving from the bed and pushing ourselves to freshen up by walking. This walking involves Force, which enables us to move forward by pushing the ground backwards.

Force is an external effort used in stretching, compressing, pushing, pulling, etc.; force may help an object move, rest, and change its speed or direction. Also, it even changes the object’s shape or size.

Definition and Examples of Force

There are many definitions for Force in Physics. Force is nothing but the interaction between two objects.

Definition of Force in Physics: “The push or pull on an object with mass that causes it to change its velocity is known as Force.”

If we observe our day-to-day activities, we can encounter many examples of Force. Some of the Force examples are given below:

1. If we want to walk in a forward direction, we require Force.
2. To stand steady on the ground, we require Force.

3. To move an object, we require Force.
4. While travelling in a bus, Force is applied.

Force Formula

Force can be calculated by using the formula,

\(F = m \times a\)

1. Where F is the Force applied on an object,
2. m is the mass of the object on which the Force is applied,
3. and a is the acceleration produced in the object by the Force.

Effects of Force

 The Force has different effects and they are explained in detail below:

1. Force may bring an object at rest into motion

For example, when we push a chair, it moves to some distance. So, by pushing the chair, we apply force to the chair. Similarly, when we kick a football, it comes into motion. So, here, by kicking the football, we are applying force.

2. Force may stop a moving object

For example, when we apply brakes to a moving bicycle, it stops. By applying brakes, we are applying force to stop the moving bicycle. Similarly, when a goalkeeper catches a football, he applies force to stop the moving football.

3. Force may change the speed of a moving object

For example, the ball rolling on the floor slows down gradually. Here, the floor applies frictional force to the rolling ball to reduce its speed. Similarly, we can decrease the speed of a moving car by applying breaks or increase the speed by accelerating the car. So, while applying the brake or pushing the accelerator, we are applying force to change the car’s speed.

4. Force may change the direction of motion of the moving object

For example, when the moving cricket ball is hit by a bat, the direction of motion of the ball changes. When a player on the ground kicks the moving football to another player, the player changes the direction of motion of the football. Here, by kicking, the player is applying force on the moving football to change its direction.

5. Force may change the shape and size of the object

For example, when we squeeze a ball, its shape and size change until we stop applying the force. Thus, by squeezing the ball, we apply force in multiple directions to change its shape and size.

Similarly, when we stretch or compress a spring, the shape, and size of the spring changes. Here, stretching or compressing is the force being applied to the spring to change its shape and size.

What is Applied Force?

When force is acting on an object, force is said to be applied to it. For example, the ball rolling on the floor experiences a frictional force, which may eventually stop the motion of the ball and bring it to rest. So, in this case, the floor is applying force on the rolling ball.

Unit of Force

Force is measured in newton in the SI system and in dyne the CGS system of units. One newton is the amount of force that can produce an acceleration of \(1\,{\rm{m}}\,{{\rm{s}}^{ – 2}}\) on an object of mass \(1\,{\rm{kg}}.\)
So, when mass is \(m = 1{\mkern 1mu} {\rm{kg}}\) and the observed acceleration is \(a = 1\,{\rm{m}}\,{{\rm{s}}^{ – 2}},\) then the applied Force \(F = 1\,{\rm{N}}{\rm{.}}\)

Types of Force

There are two types of Forces:

1. Contact Forces
2. Non-Contact Forces

Contact Forces

The forces that act only when there is physical contact with the body are known as contact forces.

For example, the frictional force that acts on a ball rolling on the floor is in a direction opposite to the ball’s direction of motion. Other examples of contact forces are mechanical force, normal reaction, muscular force, etc.

Non-contact Forces

The forces that act without making any physical contact with the body and act through intermediate space are called non-contact forces. 

For example, the gravitational force acts on a body in its field without establishing contact with it. Other examples of non-contact forces are electrostatic force, magnetic force, etc.

Balanced & Unbalanced Forces

Forces can be balanced or unbalanced. Let us understand what are balanced and unbalanced forces.

Balanced Forces 

If the resultant of all the forces acting on a body is zero, then the forces are called balanced forces. 

For example, when we push a table from both sides with equal force, the table stays where it is. The reason is we are applying balanced forces to it. 

When we hold a suitcase steadily, the resultant of the force we applied on the suitcase and the gravitational pull of the Earth on the suitcase is zero in the vertical direction. Hence, the suitcase is held steadily in a vertical manner.

The effects of force may not be visible when the forces are balanced.

Unbalanced Forces

If the resultant of all the forces acting on a body is not zero, then the forces are called unbalanced forces. 

For example, we push a table from one side, the table starts to move. Here, the resultant of the force applied by us and the frictional force is not zero, so the table at rest comes to motion. 

In a tug of war, the centre of the rope changes its position towards the team pulling with more force. So, if the centre of the rope is shifting position, then the forces applied by the teams on the two sides are not the same and hence are unbalanced forces which makes the centre of the rope shift to either side.

So, when we apply unbalanced forces, the effects of force may be seen.

Solved Examples on Force

Q.1. What would be the acceleration of a block of mass \({\rm{4}}\,{\rm{kg}},\) if a net force of \({\rm{20}}\,{\rm{N}}\) is acting on it?
Sol:
Given,
Mass \(m = 4\,{\rm{kg}}\)
Net force acting \(F = 20\,{\rm{N}}\)
We know net force acting \(F = m \times a\)
\(\Rightarrow a = \frac{F}{m} = \frac{{20\,{\rm{N}}}}{{4\,{\rm{kg}}}} = 5\,{\rm{m}}\,{{\rm{s}}^{ – 2}}\)
\(\therefore \) Acceleration of the block will be \(5\,{\rm{m}}\,{{\rm{s}}^{ – 2}}.\)

Q.2. A table of mass \({\rm{10}}\,{\rm{kg}},\) is being pushed by two students from opposite ends with forces \({\rm{20}}\,{\rm{N}}\) and \({\rm{30}}\,{\rm{N}}\) simultaneously. Find its acceleration.
Sol:
Given,
Mass of the table \(m = 10\,{\rm{kg}}\)
Force applied by the students \({F_1} = 20\,{\rm{N}}\) and \({F_2} = 30\,{\rm{N}}\)
Net force acting \(F = 30{\mkern 1mu} {\mkern 1mu} – {\mkern 1mu} 20 = 10\,{\mkern 1mu} {\rm{N}}\)
We know net force \(F = m \times a\)
\(\Rightarrow {\rm{a}} = \frac{F}{m} = \frac{{{\rm{10}}\,{\rm{N}}}}{{{\rm{10}}\,{\rm{kg}}}} = 1\,{\rm{m}}\,{{\rm{s}}^{ – 2}}\)
\(\therefore \) Acceleration of the table is \(1\,{\rm{m}}\,{{\rm{s}}^{ – 2}}.\)

Summary

The article clearly explains the types of actions produced by the application of force, the formula of force, units used to measure the force as well as the types of forces. Force is an external effort utilised in stretching, compressing, pushing, pulling, etc. Furthermore, Force may help an object rest, move, or change its direction, speed, shape, size of the objects, etc. There are two types of force, contact and non-contact forces. It is also important to note that force is a vector quantity that has both direction and magnitude. The applications of force includes setting the motion of any object at rest, stopping any object in motion.

Study Materials On Embibe

Make the use of following study materials from Embibe which will definitely help you in your exams:

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Class 8 Mock Test Series	Class 8 Practice Questions
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JEE Main Mock Tests  (Class 11-12 PCM)	JEE Main Practice Questions  (Class 11-12 PCM)
NEET Mock Tests  (Class 11-12 PCB)	NEET Practice Questions  (Class 11-12 PCB)

FAQs on Force

The frequently asked questions on Force are given below: