Unit of Momentum

What is Momentum?

Momentum is a term that is highly used in sports. When it is said that a team has momentum, it is a bit difficult to defeat the team. Momentum is a term that is associated with Physics, and it means the amount of motion contained in a body. When an object is in motion, it is said to have some momentum.

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In simple words, momentum is defined as "mass in motion". All the objects possess some mass, and when an object moves, it has momentum, i.e., it has its mass in motion. The momentum of an object depends upon two parameters, firstly the mass of the object and secondly the velocity at which the object is moving. So momentum depends upon the mass and the velocity of the object.

Derived Unit of Momentum

In mathematical terms, the momentum of an object is the product of the mass of the object and its velocity.

Momentum = mass * velocity

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In physics, the momentum of an object is denoted by 'p'. So the equation can be written as,

p = m * v


m = mass of the body, and

v = velocity of the body

The above equation describes that the momentum of a body is directly proportional to the mass & its velocity.

The si unit of momentum in physics is the product of units of mass and velocity. The unit of mass is kg, and that of velocity is m\[s^{-1}\]. Hence, the SI unit of momentum is kgm/s⁻¹.

Other Momentum Units

Let us consider a situation in which the applied force is equal to the rate of change of momentum of the object. So,

Force = rate of change of momentum


Force = (change in momentum)/(time interval) then, 

Change in momentum = Force * (time interval). 

Hence, the SI unit for momentum in physics can also be Newton-second (Ns).

In the CGS system, the mass of an object is considered in grams, and velocity is considered in terms of centimeters per second. Therefore, the unit of momentum is gram-centimeters per second (g⋅cm/s).

The standard unit of momentum is kg*m/s. There are some other units of momentum viz: kg*mi/hr, kg*km/hr, and g*cm/s. In each of these units, the unit of mass of the object is multiplied by the unit of the velocity of the object.

FAQ (Frequently Asked Questions)

1. Is Momentum a Vector Quantity?

Ans Yes, momentum is a vector quantity. It has both magnitude and direction. To understand this, the latest country football having 4 kg mass is moving in the east direction at a speed of 2 m/s. To describe the momentum of football, consider both the mass and velocity of the football. It is not just enough to say that the momentum of the football will be 8 kg*m/s, as this mentions only the magnitude and not the direction in which the football moves.

Since momentum is a vector quantity, it is important to mention the direction of motion of the football while describing its momentum. We know that the velocity vector will be in the same direction in which the object is moving, then the momentum of the photo of all can be said to be 8 kg*m/s eastward. 

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2. Guide to the Momentum Equation.

From the definition of momentum, it can be concluded that the mass and velocity of the object are of equal importance for calculating momentum. If an object has a higher mass and is moving with higher velocity, its momentum will also be higher. Let us consider a truck and a bike is moving at the same speed. 

Since the truck has more mass as compared to the bike, the momentum of the truck will be more. What is the truck at rest? Then the momentum of the bike will be greater than that of the truck. This is because the momentum of the truck will be zero, as its velocity is zero. Objects at rest don't possess any momentum. 

Now, let us consider two bikes of the same mass but moving at different speeds. The bike, which has greater speed, will have more momentum than the bike, which has less speed. This is because; the product of the mass with the velocity of the bike of greater speed will be greater than the product of mass with the velocity of the bike at a smaller speed.

The equation of momentum talks about the overall mass of the object. 

Consider a car of 100 kg loaded with 20 kg of materials, and moving with 5 m/s. 

Then the momentum of the car will be 120*5, i.e., 600 kg*m/s. 

Consider another car of mass 100 kg and loaded with three materials of 20 kg each, and moving with 5 m/s. 

In this case, the momentum of the car will be 800 kg*m/s.

This shows that the doubling or tripling of mass doubles or triples the net momentum of the object.

3. What is the Conservation of Momentum Principle?

According to the principle of conservation of momentum, the total momentum of two objects in an isolated system is the same before the collision and after the collision. Momentum is transferred between the objects of an isolated system during the collision and is not destroyed in the process. For example, while kicking a football, the momentum from our foot is transferred to the football.

Momentum depends on the type of collision. There are three types of pollution. They are elastic collisions, perfectly inelastic collisions, and partially inelastic collisions.

4. What is the Dimension of Momentum, and how is it Used?

Momentum is the vector sum of the mass of the object and velocity of the object. If the SI unit of velocity is m/s and that of mass is kg, then the unit of momentum is Kgm/s. The dimensions of momentum are MLT⁻¹.

Momentum is a beneficial quantity of energy. Here, the total linear momentum of an isolated system doesn't change and is therefore conserved. Now, there is a similar conservation rule angular momentum. This works similarly to linear momentum in a rotating system.