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• CBSE Physics Class 8 Notes

# Types of Forces

Forces are an external cause that makes a body move, stop, and increase its velocity and other. There are various types of forces in physics and they are generally classified into two categories that are, Contact Force and Non Contact Force.

In general, we define a push and pull as a force, and force is required for the proper working of the cosmos. There is a force between the fundamental particles and also between the galaxies. All these types of forces are caused by various reasons and in this article, we will learn about the types of forces, examples, and others. Before starting with the types of force we must first learn What is force. We have to study types of forces in class 8.

## What is Force?

A push or pull is defined as a force. Force always acts between two bodies that interact with each other. It is a vector quantity and has both magnitude and direction. The magnitude of the force tells us the strength of the force and the direction of the force tells us in which direction the force is applied.

Various types of forces are calculated using various formulas and the main formula used to calculate the force acting on the body of mass ‘m kg’ and accelerating at ‘a m/s2 is,

F = ma

Unit of Measurement of Force

The SI unit of measurement of force is Newton (N). Unit of force in MKS system is kgm/s2. Other unit for measuring force is Dyne.

## Different Types of Forces

There are various types of forces that we deal around us. But all those forces can be easily categorized into two types based on the contact between the object and the surface, that are,

• Contact Force
• Non-Contact Force

Now let’s learn about them in detail.

### Contact force

Contact force is the force acting between two surfaces in contact and is further categorized into various types that are,

• Muscular Force
• Frictional Force
• Normal Force
• Applied Force
• Tension Force
• Spring Force
• Air Resistance Force, etc.

### Non-Contact Force

The force that act between two bodies that are not in contact with each other is called the Non-Contact Force. Non-Contact Force is further classified into various categories that are,

• Electrostatic force
• Gravitational force
• Magnetic force
• Nuclear Force, etc.

## Contact Force

A contact force is any force that requires a contact to occur or in simple words, we can say that it arises during the motion of one object over the surface of another. Contact forces are generated only when in contact and are responsible for the most visible actions between macroscopic collections of matter. Pushing a car up an inclined surface or kicking a football across a room or in a playground or pushing any block from one place to another place or shifting large blocks from one place to another are some everyday examples where contact forces are at work.

The various types of contact force are shown in the image added below,

### Frictional Force

Friction is a force between two surfaces that are sliding, rolling or dragging across each other. For example, If we try to push an object like book along the floor, friction makes this difficult. Frictional force or opposing force always works in the direction opposite to the direction in which the object is moving, or trying to move. Friction always slows the speed of a moving object down.

The amount of frictional force exerted depends on the materials of which the two surfaces are made up of. As we increase the extent of roughness in the surface, more friction is produced. Friction also produces heat.

Example of Frictional Force

Various example of frictional force are,

• Frictional force is a useful force because it prevents our shoes from slipping on the floor when we walk and stops car tyres from skidding on the road.
• When you walk, friction is caused between the thread of shoes and the surface of the ground. This friction acts to grip the ground and prevent sliding on the road.
• Players use spikes in their shoes to enhance the friction between the ground and the shoes so that they donâ€™t slip.
• Players use gloves during batting to increase the friction and decrease the chances of slipping the bat from their hand.

### Friction Force Formula

The force of friction is calculated by using the following formula

F = Î¼N

where,

• F is Force of Friction
• Î¼ is the Coefficient of Friction
• N is the Normal Reaction Force

### Muscular Force

Our muscles exert a force on the other body when we try to lift it, bend it or in any way try to disturb its state of rest. This force exerted is called Muscular force. Many activities like lifting an object, walking on the ground, running, bending, boxing requires muscular force.

Example of Muscular Force

Various example of muscular force includes,

• Muscular forces can also be required in Strolling, lifting, getting up from a seat, crossing a leg.
• In a game of tug of war, the team which pulls the rope with a greater force wins as the rope goes in the direction of greater force.
• Whenever we are to lift a book or any object we need to apply a force that is greater than the reaction force exerted by the object.

A man pushing a block with muscular force is shown in the image added below,

### Normal Force

The reaction force applied by any object that balances the gravitational force of the Earth is called the Normal force. This force is called the normal force as it is always applied to the normal of the surface. Suppose we observe a bag lying on a thetable then the gravitational force acts on the bag in the downward direction this force is balance by an equal and opposite force called the Normal force that acts normal to the surface of the bag.

### Applied Force

The force applied to a person or an object that changes the speed, shape, and direction of the object is called the applied force. This force is the force of push or pull that is applied to an object.

### Tension Force

The force experienced in the string of a stretched string is the example of the Tension force. Suppose a mountanier climbs a mountain using a rope then his/her weight is balance by the tension force in the string.

### Spring Force

The force of compressed or stretched string is called the spring force. When we stretch or compress a string its stores some energy and this energy is responsible for the spring force.

### Air Resisting Force

The force experience by any object moving in the air is called the air resistance force. This is a type of Frictional force, suppose we drive our bike on a windy day against the wind then the wind apply a resisting force on our bike called the air resisting force.

## Non-Contact force

A non-contact force is a force that acts on an object without coming physically in contact with it. Gravity is the most familiar non-contact force, which confers weight. In contrast, a contact force is a force applied to a body by another body that is in contact with it or in other words, Forces that arise without the contact of 2 or more objects involved. The types of non-contact forces are:

• Gravitational Force
• Magnetic Force
• Electrostatic Force
• Nuclear Force

### Gravitational Force

Gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matters. All bodies have a weight on Earth, or downward force of gravity, proportional to their masses. Gravity is measured by the acceleration that it gives to freely falling objects. In other words, Gravitational force is a force exerted by the earth on all objects on it. Gravitational Force surrounds us everywhere we are. It is present when we are sitting, playing, walking, throwing, and everywhere. Not only Earth but any other massive celestial body exerts a gravitational pull. It can be greater or equal to or lesser than Earthâ€™s gravitational force, but it is present to some extent. Since the bodies with a greater mass attract everything towards us hence there is a gravitational pull on anywhere we are on if it has a mass much greater than our weight.

Example of Gravitational Force

• When a ball is thrown up, it falls to the ground because of gravitational force.
• Water always flows downwards because of gravitational force.
• When we throw an apple up it comes down because of gravitational force.
• Any fruit falls in a downward direction always it is also due to gravitational force.

### Gravitational Force Formula

It is denoted by the equation,

F = G(m1m2)/r2

where,

• F is Gravitational Force
• G is Universal Gravitational Constant
• m1 and m2 are masses of two Bodies
• r is the distance between Two Masses

### Magnetic force

Attraction or repulsion that arises between electrically charged particles because of their motion is called magnetic force. The magnetic force is a consequence of electromagnetism, one of the four fundamental forces of nature, and is caused by the motion of charges.  In simple words, two objects containing charge with the same direction of motion have a magnetic attraction force between them. If the two objects have opposite charges then they repel each other.

### Magnetic Force Formula

It is calculated by the given formula,

F = qVB sin Î¸

where,

• F is the Magnetic Force
• q is the Charge of Moving Particle
• B is Magnetic Field
• Î¸ is angle between Velocity and Magnetic Field Vectors

### Electrostatic Force

The force caused due to electric charges in an attractive and repulsive manner between the particles is called electrostatic force. The force between stationary charged bodies is conventionally known as the electrostatic force. It is also referred to as Columbaâ€™s force. In simple words, Electrostatic force is the force that exists between electrically charged particles or objects at rest.

Examples of Electrostatic Forces

Various examples of the electrostatic force are,

• When we rub a small paper piece with the oil in our head with the help of a comb it attracts the paper as shown in the image added below, this is because of the electrostatic force.

• Balloons always get attracted towards another balloon when one of them is rubbed with hair.
• When we iron silk clothes they often cling together after some time due to electrostatic charges.
• Lightning is also considered an example of electrostatic force.

### Electrostatic Force Formula

Electrostatics force is calculated by using the formula,

F = k (q1q2)/r2

where,

• F is the Electrostatic Force of Attraction
• k is Constant of Proportionality
• q1 and q2 are the charges of two Bodies
• d is the distance between the two Bodies

### Nuclear Force

The Force experienced inside the nucleus of an atom is called the nuclear force and this force is only attractive in nature. This force is responsible for binding the protons and neutrons of nucleus together. They are one of the strongest force in the universe.

### Weak Forces

Forces that are required for the decay of neutrons are called weak forces. The neutron in weak force decay into protons and emit a electron and a antineutrino. The weak force works in even a smaller distance such as 1/10 th distance of the diameter of proton.

## Examples on Force Formula

Example 1: What is the frictional force on an object if the coefficient of friction is 0.50 and the normal reaction offered is 60N?

Solution:

As we know,

F = Î¼N

Given,

• N = 60N
• Î¼ = 0.50

F = (0.5)(60)

F = 30 N

Hence the frictional force is 30 N

Example 2: What is the coefficient of friction if the frictional force exerted is 60N and the normal reaction offered is 80 N?

Solution:

As we know,

F = Î¼N

Given,

• N = 80 N
• F = 60 N

Î¼ = F/N

Î¼ = 0.75

Hence, the coefficient of friction is 0.75

Example 3: What is the normal reaction if the frictional force exerted is 50N and the coefficient of friction is 0.25?

Solution:

As we know,

F = Î¼N

Given,

• F = 50 N
• Î¼ = 0.25

N = F/Î¼

N = 50/0.25

N = 200 N

Hence, the normal reaction offered is 200 N

Example 4: What is the gravitational force on two bodies of masses 2kg and 4kg respectively and the universal gravitational constant (G) being with the separation between them being 4 m?

Solution:

As we know,

F = G(m1m2)/r2

Putting the values from the question we get,

F = (6.6 Ã— 10-11 Ã— 4 Ã— 2)/42

F = 3.3 Ã— 10-11 N

Example 5: What is the gravitational force on two bodies of masses 4 kg and 6 kg respectively and the universal gravitational constant (G) being with the separation between the two bodies being 2 m?

Solution:

As we know,

F = G(m1m2)/r2

Putting the values from the question we get,

F = (6.6 Ã— 10-11 Ã— 4 Ã— 6)/22

F = 39.6 Ã— 10-11 N

Example 6: What is the electrostatic force between two charges of charge 4C and 5C which are at a distance of 4m with constant of proportionality 1?

Solution:

As we know,

F = K(q1q2)/r2

Putting the values from the question we get,

F = (1 Ã— 4 Ã— 5)/42

F = 1.25 N

Example 7: What is the electrostatic force between two charges of charge (-3C) and (-6C) which are at a distance of 4 m with constant of proportionality 1?

Solution:

As we know,

F = K(q1q2)/r2

Putting the values from the question we get,

F = {1 Ã— (-3) Ã— (-6)}/42

F = 1.125 N

Example 8: What is the magnetic force exerted by a charge of 3 C moving with a velocity of 6m/s in a magnetic field of 6 T and the value of sin Î¸ = 1/2?

Solution:

Magnetic forces can be calculated by the following equation

F = qvBsinÎ¸

Given,

• q= 3C
• B= 6 T
• sin Î¸ = 1/2
• v= 6m/s

Putting the values we have,

F = 3 Ã— 6 Ã— 6 Ã— 1/2

F = 54 N

Hence the magnetic force is 54 N

Example 9: What is the magnetic force exerted by a charge of 4C moving with a velocity of 8m/s in a magnetic field of 8T and the value of sin Î¸ = 1?

Solution:

As we know,

Magnetic forces can be calculated by the following equation

F = qvBsinÎ¸

Given,

• q = 4 C
• B = 8 T
• sin Î¸ = 1
• v = 8 m/s

Putting the values we have,

F = 4 Ã— 8 Ã— 8 Ã— 1

F = 256 N

Hence the magnetic force is 256 N

## Types of Forces – FAQs

### 1. What is a Force?

A push or a pull is called a force and the force is responsible for the change in shape, size, speed, and direction of an object.

### 2. What are the Different Types of Forces?

Forces are of different types based on the mode of contact and nature of particles responsible. In general the force are of two types, Contant Force and Non Contact Force.

### 3. What are 4 Types of Forces?

The 4 main types of forces that are observed in nature are,

• Gravity (Gravitational Force)
• Electromagnetism
• Strong Nuclear Force
• Weak nuclear Force

### 4. What are the 7 Types of Forces?

The seven different types of contact force are,

• Normal Force
• Applied Force
• Muscular Force
• Frictional Force
• Air Resistance Force
• Tension Force
• Spring Force

### 5. What are the Types Classification of Forces?

In physics the force are generally classified into two categories that include,

• Conatct Force
• Non-Contact Force

### 6. What is Formula of Force?

The force acting on a body of mass ‘m’ that is moving with an acceleration ‘a’ is calculated as,

F = ma

### 7. What is Unit of Force?

The unit of force is Newton and it is also measured in Kgm/s2

### 8. What is Friction Force?

Friction force is a type of the contact force and this force always oppose the motion that produces it. Friction force is produced by the rough and crust surfaces of the bodies.

### 9. What are 2 Types of Forces?

The 2 Types of forces are,

• Contact Forces
• Non Contact forces

### 10. What are Types of Force class 8?

Types of Forces class 8 are of two types, contact force, i.e. the force that acts on the object that are in contact such as Friction and Non-contact Force that works on the object that are not in contact such as Gravitational force.

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