Momentum

Basic Principles

Momentum is a vector quantity, and it is the product of an object’s mass and its velocity.
It has both magnitude and direction.
The SI unit of momentum is kg m/s.
Momentum can be described as ‘mass in motion’ - all objects have mass; so if an object is moving, then it has momentum.

The Principle of Conservation of Momentum states that the total momentum of an isolated system remains constant if no external forces act on it.
This means that the total momentum before an event must be the same as the total momentum after the event.

In collisions, momentum is transferred from one body to another.
There are two types of collision: elastic and inelastic.
In an elastic collision, both momentum and kinetic energy are conserved.
In an inelastic collision, momentum is conserved but kinetic energy is not as some is transferred to other forms such as heat and sound.

Impulse is defined as the change in momentum of an object when the object is acted upon by a force for an interval of time.
It can be calculated by multiplying the force (in newtons) acting on the object by the time (in seconds) that the force is acting: Impulse = Force x Time
Impulse is a vector quantity and it has the same direction as the change in velocity.
It can also be obtained by finding the area under a force-time graph.
Hence, Impulse-Momentum theorem relates impulse and momentum by stating that the change in momentum of an object equals the impulse applied to it.

Newton’s Second Law of Motion is closely related to the concept of momentum. It can be seen as a statement of the conservation of momentum for an isolated system.