What is a force?

What is a force? If you’ve placed a pencil at a table, do you think it will ever move on its own? For a moment, if we ignore surface friction, air pressure and gravity and then we set the pencil in motion; do you think it will ever come to rest on its own? Well, answer to both the question is NO. In the previous one, the pencil can move, accelerate rather I’d say, only when some unbalanced force is applied to it. And in the second example, the pencil will not come to rest ever provided that applied by some unbalanced force. This is what we’ve learned from Newton’s First Law of Motion. Therefore force can be defined as:

Force is an agent which tends to produce a change in the state of rest or of uniform motion of an object. It creates an acceleration in a body. We can also say it is a push or a pull of one object on another when both objects interact with each other. When two objects interact, then a force acts upon each of the objects and when there is no interaction, objects do not feel any kind of interaction, Interaction is the vital thing for the existence of forces.

One thing you must always make sure that force doesn’t produce motion, it creates acceleration only.

Types of forces

There are two types of forces on a broad scale.
  • Contact Forces
  • Non-contact Forces (Action-at-a-distance forces)

Contact Forces:

Contact forces are those types of forces when two bodies interacting with each other physically come in contact with each other. They act through a point of contact between two interacting bodies and this contact could be momentarily in the shape of impulse or continue for some period of time. For example, if a boy kicks a football, then the boy is applying force on the football by coming in physical contact with the football. Examples of contact forces include applied forces, frictional forces, normal forces, air resistance forces and tensional forces.

Applied Forces

Applied force is a force that is applied by one object on another. If a boy is pulling a cart through the floor and he is applying a force on the cart to accelerate it and this force is applied force.

Frictional Force

The frictional force is a force that comes into play two bodies are sliding over one another and its purpose is to oppose the motion. This force is applied by the surface over which an object moves or try to move. Because every surface has some kind of roughness in the shape of bumps and ridges, therefore, when these microscopic peaks and valley come in contact with each other they try to hinder the motion of an object due to intermolecular attractive forces between molecules of different surfaces.

Normal Force

The normal force also called a support force, is a force which supports the weight of a body on a supporting surface. This force is always equal in magnitude and opposite in direction to the weight of an object. We are standing on the ground, our weight is acting downward, and an equal force acting upward to support our weight is the Normal force.

Tension Force

The tension force is a force that acts along a string or cable which it is being pulled by forces acting from its opposite ends. For example, if we attach a weight at one end of a string and hang it somewhere, then the force that acts along in the string in the direction opposite to the weight is tension force. If this force gets equal to weight then the body gets in equilibrium.

Air resistance

Air resistance is a force that opposes the motion of an object when it tries to move through the air. Although it is quite noticeable for objects traveling at a very high speed, yet its magnitude is negligible in everyday life

Non-contact Forces (Action-at-a-distance forces)

These are the type of forces between two interacting objects when they do not come in physical contact with each other. Non-contact forces include gravitational forces- which is a force of attraction between two bodies having mass, electric forces-force of attraction between the nucleus and revolving electrons in orbits, and magnetic forces which are attractive or repulsive forces between two magnets separated by some distance.

The Newton (unit of force)

Force is a measurable quantity and every measurable quantity has a unit. Force is measured using a standard metric unit called the Newton (N). And one Newton is defined as the amount of force required to produce an acceleration of one meter per second in a body of mass one kilogram. Mathematically it is stated as
1 Newton = 1 kg • m/s2


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