Contact and Non Contact Forces

A type of force that acts between two surfaces in contact is a contact force, while the force that acts between the two surfaces not in contact is a non-contact force.

Like we study that “traction is the friction force that acts between a drive wheel and the road surface. So, if you lose traction, you lose road grip.” This means that a contact is required for the frictional force to happen, then why do we categorize force into non-contact?

Do you think there are any forces that act without the need of bringing two objects or surfaces together? If yes, then how?

This page will answer all your queries. You will also get to know various examples to understand the difference between contact and non-contact force.

Contact Force Definition

A force that acts only when there is physical contact between two bodies. 

We learned about Newton’s second law of motion. It says that by applying force to the body of mass ‘m’, the body starts accelerating.

If the body is of mass ‘m’ and the acceleration it attains after being subjected to force is ‘a’, then the equation for the force becomes:

F = ma

However, one more thing happens is, when we apply force on the body, it gains momentum, so the rate of change of momentum is equal to the force applied. The equation for the same is as follows:

We know that Δp = mΔv or m = \[\frac{\Delta p}{\Delta v}\]

F = m\[\frac{\Delta v}{\Delta t}\]   or m = F\[\frac{\Delta t}{\Delta v}\]

Now, equating both the values of m here:

So,  F\[\frac{\Delta t}{\Delta v}\] = \[\frac{\Delta p}{\Delta v}\]

We get F =\[\frac{\Delta p}{\Delta t}\] (Here,\[\frac{\Delta p}{\Delta t}\] change in momentum per unit time and its unit is kg-m/s.)

Types of Contact Forces

Below is the list of the types of contact forces:

• Surface tension

• Air resistance

• Friction

• Upthrust or Buoyancy force

• Drag force

• Applied force

• Normal force

• Muscular force

Examples of Contact Forces with Explanation

• Example 1: 

Throw a football and it flies in the sky and then reaches the ground.

In this example, you can observe two types of forces. 

Firstly, under the contact force of our kick, it makes a vertical motion, then executes a projectile motion, and now, under the effect of air resistance or simply friction, the ball slows down and eventually comes to rest, i.e., on the ground. 

• Example 2: 

Stretch the spring from its resting position, it will start oscillating from its mean position. However, after some time, under the effect of restoring force, the spring comes back to its original position.

Now, let’s take some contact force examples where you can definitely find the difference between contact and non contact force.

• Example 3: 

You all love paragliding, bungee jumping, and much more adventurous activities. All these work under the effect of the contact force.

Non-Contact Force Definition

Non-contact force is a type of force that acts on the object, without any physical contact with it, the most familiar type of non-contact force is gravity which confers with the weight. In comparison to the contact forces, only there are a few non-contact forces. Some of the examples of non-contact forces are:

• Gravitational force

• Magnetic force

• Electrostatics

• The nuclear force - (there are two types of strong and weak nuclear force).

Types of Non-contact Forces - Explanation of Examples

1. Gravitational Force

This type of force is responsible for bringing the items that are tossed back to the air. When any object is at rest on the surface, it exerts a downward force that is equal to its weight and this downward force is known as the gravitational force.

Gravitational force is a type of attractive force that exists between all bodies having the mass, gravitational force of the sun keeps the sun and all the other planets of the solar system in a fixed orbit. Gravitation force is not required to be contacted to excerpt its downward force.

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There are many advantages of non-contact gravitational force, it is a kind of constant force that keeps things in place. Gravity keeps our muscles and bones up and working, and it allows the earth to retain its atmosphere. And gravity is able to store some energy as potential energy, it allows it to harness, its example is a water dam.

2. Electrostatic Force

This force is very similar to the gravitational force, the main difference here is that gravitational force acts between masses, and an electrostatic force acts between the two charged bodies.

This force can be generated by rubbing the comb on your clothes and then holding it near tiny pieces of paper, you can observe bits of paper standing on their end attracted to the comb. Everything is made of tiny positive, negative and neutral particles, the opposite charges attract each other and the like charges repel, this is the result of the electrostatic forces.

3. Magnetic Force

Consider, if you push the ends of the magnet together the second magnet will bounce off, this is the result of the magnetic force. It is also responsible for the attraction of iron by the force of magnets.  The magnetic force of the magnet goes on decreasing with an increase in the distance of the magnets.

The different sorts of attraction in magnetism are:

• Diamagnetism

• Ferromagnetism

• Paramagnetism

• Antiferromagnetism

• Electromagnetism

4. Strong Nuclear Force

It is a short-distance force, which takes place between the fundamental particles within the nucleus. A strong nuclear force is charge independent and acts equally between a proton and a proton, and a neutron and a neutron, and a proton and a neutron, the strong nuclear force is the strongest force in nature. Because its range is small, strong nuclear force mediates both nuclear fission and fusion reactions.

5. Weak Nuclear Force

This force mediates the beta decay of a neutron, in which the neutron decays into a proton. And in this process, it emits a beta particle and an uncharged particle called the neutrino. It plays an important key role in the supernova, both the strong and weak forces form an important part of quantum mechanics

Examples of Non-Contact Forces

Various Non-Contact Force examples from our daily life are provided below.

• An apple falling down from a tree is one of the best examples of the gravitational force, which was observed by Newton.

• Iron pins get attracted to the magnet bar without any physical contact, due to the magnetic force.

• The falling of raindrops on earth is also an example of non-contact force, which acts due to the gravitational force.

• The charging of the hair and attraction of paper bits towards it you would have observed generally is due to the electrostatics.

• When two magnets are placed close to each other is also an example of non-contact forces.

• The ball falling freely in the virtue of gravity towards the earth is due to the gravitational force.

• Even leaves falling from the tree is an example of non-contact force.

• Electromagnetism is another example of non-contact force.

• You can see various examples of electrostatics, which shows the attraction of small material towards an object.

• When an electric current is passed through iron converting it into an electromagnet, it attracts iron and particles towards it, thus, displaying non-contact force properties.

Difference Between Contact and Non-Contact Forces

From the above text, we understand that a force that requires contact and no linkage of the field is a contact force, while that which doesn't require contact and has a linkage with the field is a non-contact force.