Momentum
Momentum is a fundamental concept in physics that describes the motion of an object. It is defined as the product of an object's mass and its velocity. Mathematically, momentum (p) is given by the equation:

p = m * v

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

Momentum in a System
When two or more objects interact with each other, the total momentum of the system is conserved before and after the interaction. This is known as the law of conservation of momentum. In other words, the total momentum of the system before a collision is equal to the total momentum after the collision.

Collision Scenario
In this scenario, we have two bodies with masses of 1kg and 2kg respectively. They are moving in opposite directions with a speed of 5m/s. Let's calculate the total momentum of the system before the collision.

Calculating the Momentum
To calculate the total momentum of the system, we need to find the momentum of each object and add them together.

For the first body with a mass of 1kg:
Momentum = mass * velocity = 1kg * 5m/s = 5kg⋅m/s

For the second body with a mass of 2kg:
Momentum = mass * velocity = 2kg * (-5m/s) = -10kg⋅m/s
(Note: The negative sign indicates the opposite direction of motion.)

Total Momentum
Now, we can add the momentum of both bodies to find the total momentum of the system before the collision:

Total momentum = momentum of body 1 + momentum of body 2
= 5kg⋅m/s + (-10kg⋅m/s)
= -5kg⋅m/s

Therefore, the total momentum of the system before the collision is -5kg⋅m/s.