Phoenix Business Daily

What's the difference between INERTIA and MOMENTUM?

I know they're not the same but I just can't tell the difference. How are inertia and momentum related? thanks!!

Public Comments

1. momentum, at least the definition of the linear momentum of a particle, is defined as the product of the particles mass and velocity inertia is the tendency of an object to resist any attempt to change its velocity The fact that momentum contains the product of the particles mass and velocity is purely trivial. But even though this is trivial, it does provide a person with much information regarding properties of that particle. An example of this usefulness is when calculating the results of multi-particles collisions and other problems that are solved when applying the rules of conservation of momentum. Inertia on the other hand is useful when solving problems using Newton’s first law of motion such as when you apply a defined force on a particle, it will result in acceleration in an appropriate direction with a specific magnitude.
2. Momentum of a body is defined as the product of its mass and its velocity. Inertia is the tendency of a body to remain at rest or, if moving, to continue its motion in a straight line.
3. Newton’s first law of motion is sometimes referred as ‘Law’s of Inertia” In a reference frame which is at rest or in uniform motion with reference to a distant fixed star, we formulate the laws of physics. If a body is at rest with respect to the reference frame chosen, then it will continue to be in its state of rest till a force ( or a net force, if many forces) act on it. If a body is moving with constant (uniform) speed with respect to the reference frame chosen, then it will continue to move with the same speed in a straight line till a force (or a net force, if many forces) act on it. The descriptions in the law refer to some state and the constancy of the state is called inertia. And, hence, it is not defined as a quantity and it has no units of measurement. However, we can use other properties like mass, momentum etc to describe the state of inertia. Using the second law we know how to measure the force. F = rate of change in momentum. Momentum is the product of mass and velocity. As per Newton’s first law, the momentum may be either zero or some fixed value as long as no other force acts on it. Zero momentum corresponds to the state of rest. If we take zero momentum as the reference point to compare the inertial states of the bodies, then to bring a body to zero momentum, greater force is necessary for a body having greater momentum than for a body having lesser momentum. So we can say that the body having higher momentum is in a state of higher inertia than a body having lesser momentum. Thus momentum directly measures the inertial state of the body. Now, with out any ambiguity, we can say that momentum of a moving body is the measure of its inertia. Similarly for rotational motion the moment of momentum is the measure of its inertia. For bodies at rest, mass is the measure of its inertia.
4. Inertia is the property of a body to maintain it's motion. Momentum is it's forward motion in feet per second.