What is the difference between momentum and inertia?

Answer 1

The more momentum something has, the harder it is to stop it from moving. Momentum=Mass times velocity. Inertia is the property that states that an object at rest tends to stay in rest, while an object in motion tends to stay in motion unless acted on by an outer force.

Answer 2

Momentum is a vector property acquired by a mass in motion relative to an observer. The faster the relative motion, the greater the momentum. No relative motion, zero momentum. It is momentum that allows kinetic energy to be acquired and kinetic energy to be transferred through a collision.

Mass is not necessary to having the property of momentum. Photons, which are mass-less, also have momentum.

Inertia is a scalar property of anything that has mass. It is the property that allows a mass to acquire momentum (and kinetic energy) when a force is applied, by providing an equal and opposite force. Mass and inertia are thought to be equivalent properties of matter.

Answer 3

Inertia is the property of mass that says it takes a force to change the velocity of (accelerate/decelerate) that mass. I like to think of momentum as a measure of inertia.

Momentum = p = mv for objects with rest mass m traveling at velocity v, including zero velocity. So more mass means more momentum for any given velocity. In fact, we see next, that the force needed to change velocity of a mass (inertia) can be easily derived from momentum.

The change in momentum over time dp/dt = mdv/dt = ma = force = f; where dv/dt = a = acceleration, the change in velocity over time. In other words, good old f = ma comes from changing the velocity of a mass with momentum p = mv. And that's the force we talk about needing to overcome inertia.

If we wish to change velocity of a larger mass (M) at the same rate as the smaller mass, we have f/m = dv/dt = F/M; so that F = f (M/m), which shows it takes more force F > f to change the velocity of a larger mass than of a smaller mass. And that's all inertia says, it takes more force to change the velocity of a larger mass than a smaller mass. Which is why I like to think of momentum as just a measure of inertia even though momentum is a vector and inertia is not.

Answer 4

When talking about inertia your talking about how much energy to get something to move. When talking about momentum your talking about how much energy to get something to stop moving.