What is Force?

Push or pull of an object is considered a force. Push and pull come from the objects interacting with one another. Terms like stretch and squeeze can also be used to denote force.
In Physics, force is defined as:

The push or pull on an object with mass that causes it to change its velocity.

Force is an external agent capable of changing the state of rest or motion of a particular body. It has a magnitude and a direction. The direction towards which the force is applied is known as the direction of the force, and the application of force is the point where force is applied. The Force can be measured using a spring balance. The SI unit of force is Newton(N).

Common symbols: F→, F
SI unit: Newton
In SI base units: kg·m/s2
Other units: dyne, poundal, pound-force, kip, kilopond
Derivations from other quantities:  F = m a
Dimension: LMT-2

What are the effects of force?

In physics, motion is defined as the change in position with respect to time. In simpler words, motion refers to the movement of a body. Typically, motion can either be described as:

  1. Change in speed
  2. Change in direction

The Force has different effects and here are some of them.

  • Force can make a body which is at rest to move.
  • It can stop a moving body or slow it down.
  • It can accelerate the speed of a moving body.
  • It can also change the direction of a moving body along with its shape and size.


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Types of Force

Force is a physical cause that can change the state of motion or the dimensions of an object. There are two types of forces based on their applications:

  1. Contact Force
  2. Non-Contact Force

Contact Force

Forces which act on a body either directly or through a medium are called contact forces.

Examples of contact forces are:

  • muscular force
  • mechanical force
  • frictional force

We can make use of muscular force of animals like bullocks, horses and camels to get the activities done. The frictional force is another type of contact force which acts between a pair of a surface in contact and tends to oppose the motion of one surface over the other.

Non-Contact Force

Forces which act through spaces without making direct contact with the body are called non-contact forces.

Examples of non-contact forces are:

  • gravitational force
  • electrostatic force
  • magnetic force

The force exerted by a magnet on other magnets is called magnetic force. Magnetic force and electrostatic force act on an object from a distance, that’s the reason they are non-contact forces. The strength of gravity is an attractive force which is exerted by the Earth on objects which make them fall to the land. The weight of a body is the force which is pulled by the earth towards the centre.

Formula for Force

The quantity of force is expressed by the vector product of mass (m) and acceleration (a). The equation or the formula for force can mathematically be expressed in the form of:

F = ma


Unit of Force

  • In the centimetre gram second system of unit (CGS unit) force is expressed in dyne.
  • In the standard international system of unit (SI unit) it is expressed in Newton (N).

Solved Example on Force

How much net force is required to accelerate a 1000 kg car at 4.00 m/s2?



  • a = 4.00 m/s2
  • m = 1000kg


F = ma

= 1000 × 4

= 4000 N

What is the line of action of a force?

The line along which a force is acting on an object is called the line of action of the force. The point where the force is acting on an object is called the point of application of the force. The force which opposes the relative motion between the surfaces of two objects in contact and acts along the surfaces is called the force of friction.

Galileo experimentally proved that objects that are in motion move with constant speed when there is no force acting on it. He could note that when a sphere is rolling down an inclined plane, its speed increases because of the gravitational pull which is acting on it.

When all the forces acting on an object are balanced, the net force acting is zero. But, if all the forces acting on a body result in an unbalanced force, then the unbalanced force can accelerate the body, which means that a net force acting on a body can either change the magnitude of its velocity or change the direction of its velocity. For example, when many forces act on a body, and the body is found to be at rest, we can conclude that the net force acting on the body is zero.

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