Momentum Definition

By Momentum we mean inertia in motion. More specifically, Linear Momentum or Momentum is defined as the product of the mass and velocity of an object. It’s designated with sign p.

We will use this sign p now onwards in this topic instead of the full name of the quantity we are discussing


*Next 2 Parts of this running topic*

Impulse Momenta Theorem

Momentum meaning

While playing some sort of body-contact game, if a heavy (with more mass) but slow moving person(less velocity) pushes us, we tend to move from our initial position.

Similarly if a lighter person (less mass) comes with higher velocity and pushes us we may face the same net effect and again begin to move.

In physics, to understand this combined motion effect of mass and velocity, this quantity p comes into picture.

Momentum formula – equation

The formula or equation is written as:

p = m v

where m is the mass of the object and v is its velocity.

From the example in the beginning of this topic and the above equation, we see that p is directly proportional to the mass and velocity of an object.

As a result a heavy but slowly moving object may have a p equal (in magnitude) to that of a light but fast moving object.

SI Unit

SI unit of momentum is
Kg meter/second.

CGS unit of it is

gm centimeter/second.

Vector or Scalar?

Because the velocity v is a vector quantity with both magnitude and direction, p too is a Vector quantity.

As p is a vector, the total p of a system consisting of objects is the vector sum of the momenta of all the objects in that system.

In the next parts of this discussion we will cover impulse first. And then find out how p is related to impulse.

We will cover how Newton’s second law and equation of force come into play to derive relation between p and impulse.

Next 2 Parts


Impulse-Momentum Theorem

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