impulse in physics

What is impulse in physics and how it Works?

Impulse is defined as the force multiplied by the amount of time. When a force is applied for a certain amount of time on a particle, momentum of the particle changes (if the particle moves). Simply, the impulse in physics is the effect of both forces applied and amount of time.

Impulse is involved with our daily activities, but we do not notice it. Impulse works whenever we apply force on something and as a result that object changes position. The ball changes position when kicked in football while playing football, the ball moves away when hit with the bat in cricket, in which case impulse is working.

Is impulse in physics scalar or a vector quantity?

The vector quantity is of equal importance in both direction and magnitude. Force is a vector quantity and time is a scalar quantity, multiplication of both creates a vector quantity, i.e. Impulse is a vector quantity. Symbol of Impulse is J or Imp.

Real also: What is viscosity in Physics? How does it work? with examples.

Unit of impulse

Impulse is the change of momentum over time. So, the SI unit of impulse is N*s (Newton × second), or it can be written as kilogram meter per second. In FPS unit, the unit of impulse is pound-second (lbf*s).

What is impulse-momentum principal

The impulse-momentum theorem states that the change in momentum of an object equals the impulse applied to it, i.e J = ∆p (p=momentum)

If a constant force is applied on a particle over time, then the impulse is
Force​×time. That clearly says, if we want to increase the magnitude of impulse, we have to increase the magnitude of force or amount of time over which we apply the force.

In classical mechanics, Newton’s second law says force equals mass time acceleration, also known as force law.

Logically impulse-momentum theorem is equivalent to Newton’s second law of motion. This theorem works both in case of constant mass and changing mass. In everyday’s life example, almost in every case mass remains constant, if we apply to rockets in which fuel decrease over time, that means mass decrease over time. In both cases, this theorem works well.

Example of impulse in physics

What is specific impulse?

Specific impulse is a term used where thrush force creates. Jet engines and rockets are two main examples. Specific impulse the measure of efficiency to produce thrush using fuel. The more specific impulse of an engine, it will take less propellant (force to propel) to gain height and distance. Generally, specific impulse is measured in seconds. Car manufacturer uses this unit to show the efficiency of cars.

Suppose a jet engine has specific impulse is 100 seconds, that means it takes 100 seconds to create 1 N thrust force by using 1 N fuel (If propellent is measured in Newton or pound)

Impulse formula

Since the impulse is a measure of how much the momentum changes as a result of a force acting on it for a certain period of time.

Impulse = Force × (final time – initial time)
Impulse = Force × Δt
J = F × Δt

J = refers to the impulse
F = refers to the force of the object
Δt = refers to the change in time


The impulse in physics is the product of applied force and amount of time. It is useful when a large amount of force will apply for a very small span of time. In classical mechanics, the impulse-momentum theorem is equivalent to Newton’s second law.

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