Kinetic Kinetic Molecular Molecular

TheoryTheoryKMTKMT

KMTKMT

Newtonian Cradle:

What happens as two balls are pulled back and then released?

Why does this happen?

KMTKMTWhere the collisions between the balls elastic?

Initially Yes, because kinetic energy was transferred with each collision

Why did the balls eventually stop swinging? The collisions were not perfectly elastic, some kinetic energy was lost as heat during each collision.

KMT - AssumptionsKMT - Assumptions• Gas consists of large number of particles

(atoms or molecules)– Small, hard spheres

• Particles make elastic collisions with each other and with walls of container

• There exist no external forces (density constant)

• Particles, on average, are separated by distances large compared to their diameters- Insignificant volume; relatively far apart from each other

KMT - AssumptionsKMT - AssumptionsNo forces between particles except

when they collide – No attraction or repulsion between particles

Particles in a gas move rapidly in constant random motion– Move in straight paths, changing direction only when

colliding with one another or other objects

– Average speed of O2 in air at 20 oC is an amazing 1660 km/h! (1.6km=1mile)