Equations for Force in Physics | definition formula unit

We have already discussed Newton’s laws of motion in other three articles. We got the definition of force from Newton’s first law of motion and the formula or the equation of force was derived from the Newton’s second law of motion. In this article, we are going to discuss the definition, formula, units, dimension, types and equations for force in classical physics.

1. Definition of force
2. What is the formula for force?
3. Unit of force
4. Dimension of force
5. How many force are there?
6. Equations for force in physics

Definition of force

The Force is an external agent that is used to break the existing inertia (rest or motion) of a body. That means the applied force can make a rest body in motion and also, it can increase the velocity of a moving body. But, every force cannot move a rest body. We need to apply a sufficient amount of force to do so.

What is the formula for Force?

Newton’s second law of motion gives the formula of force. According to this law, if a force F can provide an acceleration a to an object of mass m, then the equation of the force is,

F = ma…….(1)

That means, Force = Mass × Acceleration.

This is the basic formula of force. But, there are different forms of force equation in different cases. We have mentioned those in below.

Unit of Force

The SI unit of Force is Newton (N) and the CGS unit of Force is dyne.

1 N = 105 dyne.

Dimension of Force

The dimensional formula of Force is [MLT-2]. One can derive this dimension of force from the equation-(1). This is simply the multiplication between the dimensions of mass and acceleration.

How many Forces are there?

There are four fundamental forces in the universe. These are –

• Gravitational Force
• Electromagnetic Force
• Strong Force
• Weak Force

Other forces are friction force, Tension force, Pulling force, Pushing force, centripetal force, etc. But these are not the fundamental forces.

Equations for Force in Physics

Strong force and weak force do not have accurate equations. But the Gravitational force, Electromagnetic force and other forms of these have definite equations. Popular equations of different types of forces are listed below.

Equation of Gravitational Force

If r be the distance between two point masses m1 and m2 then the Gravitational attraction force acting between the masses is

$\color{Blue}F_{g} = G.\frac{m_{1}.m_{2}}{r^{2}}$……..(2)

Where, G is the universal gravitational constant.

Equations of Electromagnetic Force

• If a point charge q is placed in an external electric field E, then the electrostatic force on that charge is F = qE. This is Lorentz force equation in electric field. Scientist Coulomb gives another form of this electrostatic force as, $\color{Blue}F_{e} = k.\frac{q_{1}.q_{2}}{r^{2}}$. This the electrostatic force between two point charges q1 and q2 separated by a distance r. Here, k is the coulomb’s constant.
• If a point charge q is moving with a speed v in an external magnetic field B, then the Lorentz equation of magnetic force on the moving charge is, $\color{Blue}F_{B} = qvBsin\theta$.

Equation of friction force

The equation of friction force is, $\color{Blue}F_{f} = \mu.N$.

Where, $\color{Blue}\mu$ is the co-efficient of friction and N is the normal reaction on the object.

Equation for centripetal force

If an object of mass m is moving in a circular path of radius r with a speed v, then the centripetal force and centrifugal force acting on the object is, $\color{Blue}F_{c} = \frac{mv^{2}}{r}$

This is all from this article on equations of force in physics. If you have any doubt on this topic you can ask me in the comment section.

Thank you!

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