Collisions are perfectly elastic
Collisions between molecules and with the container walls conserve both total kinetic energy and total momentum.
What is Collisions are perfectly elastic?
A collision in which both momentum and kinetic energy are conserved.
Key formula / rule: Kinetic Energy
Key points
- To understand the nature of molecular collisions in the kinetic theory of gases.
- To recognize the conservation principles (energy and momentum) applicable to these collisions.
- To appreciate the role of this assumption in deriving gas laws.
Common exam trap
Confusing perfectly elastic collisions with inelastic collisions where energy is lost.
Definitions
- Term
Perfectly Elastic Collision
- Meaning
A collision in which both momentum and kinetic energy are conserved.
- Term
Kinetic Theory of Gases
- Meaning
A model that explains the macroscopic properties of gases in terms of the motion of their constituent molecules.
Learning objectives
To understand the nature of molecular collisions in the kinetic theory of gases.
To recognize the conservation principles (energy and momentum) applicable to these collisions.
To appreciate the role of this assumption in deriving gas laws.
Formulae
- Name
Kinetic Energy
- Note
Total kinetic energy is conserved in perfectly elastic collisions.
- Expression
KE = 1/2 mv2
- Name
Momentum
- Note
Total momentum is conserved in perfectly elastic collisions.
- Expression
p = mv
Prerequisites
Understanding of kinetic energy (1/2 mv2).
Understanding of momentum (mv).
Basic concepts of collisions.
Newton's laws of motion.
Common mistakes
Confusing perfectly elastic collisions with inelastic collisions where energy is lost.
Forgetting that both kinetic energy and momentum are conserved, not just one.
Assuming that real gas molecule collisions are exactly perfectly elastic without any deviation.
Keywords
Kinetic Theory of Gases
Elastic Collision
Momentum Conservation
Kinetic Energy Conservation
Ideal Gas
Molecular Collisions
Practice preview
If two gas molecules collide elastically, which of the following quantities is conserved?…
easy
If the kinetic energy of gas molecules were not conserved during collisions, which of the following macroscopic properties would be most directly affected over time, assuming constant volume?…
medium
In the kinetic theory of gases, what is the nature of collisions between gas molecules and between molecules and the container walls?…
easy