# Newton's First law and KT of Gases

One of the assumptions of Kinetic Theory states that:

A gas is a substance composed of many particles flying about randomly, colliding with one another and with the walls of the container.

My instructor mention that we might be required to Know, state, and apply this theory to one of newtoms laws, without stating which one.

After thinking it over, I decided that it applied to Newton's First Law OR newtons third law:

An object in at a state of rest or uniform motion will remain at rest or in a state of uniform motion unless an force is exerted upon it.

For every actiont here is an equal and opposite reaction

The application and explation i have is this:

Since we assume that all the particles in a gas are identical and as such have identical masses, volumes and weights, when they collide with one another, they each exerts a force on the other that is equal in magnitude and opposite in direction ( 3rd law). This force sends the partcles away from each other, each following a straight path, moving at a constant velocity until it collides with another particle or the walls of the container (1st law ) and changes direction. The random nature of a particles motion comes from the continuous colliding and changing direction.

I also wanted to add this but it seems unrelated:

In a gas, each particle posses a net amount of kinetic energy. (KE) Since the collisions between particles are perfectly elastic, the net amount of KE in the gas remains constant.

However, the above explanation involves two laws, and I strongly believe he is looking for us to relate it to one. So

1) Is the above explanation accurate and acceptable?

2) Which law applies most the that assumption of the KT? And how so?

Drakkith
Staff Emeritus