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# Explain inertia and momentum in detail.

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## Inertia: Inertia is the resistance offered by an object to change its state of rest or state of motion without the application of an external force.The magnitude of force necessary to change the state of motion is directly proportional to the mass of the object. The SI unit of moment of inertia is ${\mathrm{kgm}}^{-2}$.Newton's first law is known as the law of inertia. The law states that if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.In the diagram above, when the cardboard is pulled, the coin falls into the glass. This is because the inertia of the coin maintains its state of rest and it falls into the glass due to gravity.Momentum:Momentum is the tendency of an object by which an object continues to move.Momentum increases with an increase in mass as well as with the increase in velocity of the object. The S.I unit of momentum is ${\mathrm{kgms}}^{-1}$The momentum of an object is a function of its mass $\left(m\right)$ and velocity $\left(v\right)$ with which it is moving and is expressed as,$\mathrm{Momentum}\left(p\right)=mv$ 4. Consider this example of a balloon, the particles of gas move rapidly colliding with each other and the walls of the balloon, even though the particles themselves move faster and slower when they lose or gain momentum when they collide, the total momentum of the system remains the same. Hence, the balloon doesn’t change in size, if we add external energy by heating it, the balloon should expand because it increases the velocity of the particles and this increases their momentum, in turn, increasing the force exerted by them on the walls of the balloon.

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