A ball of soft clay lands on the floor: a dull thud, a flattened base, and no bounce at all. The clay arrived with kinetic energy. The thud and the flattening are where it went.
The last lesson named the collisions that keep their kinetic energy. This lesson names the other kind.
The clay hit the floor moving, so the system had kinetic energy before the impact. After it, the clay sits still.
The kinetic energy did not vanish. It transformed: some left as sound (the thud), some became heat in the squeezed clay, and some went into deforming it (the flattened base).
When a collision transforms some of the system's kinetic energy into other forms such as heat, sound, or deformation, we call it inelastic.
A shopping cart rolls into a wall; the cart's basket dents and the hit makes a bang. Is the collision elastic or inelastic?
Most real collisions are inelastic. Crumpling fenders, thudding boxes, squeaking bumper cars: each sound and each dent is kinetic energy changing form.
Bouncing does not decide the class; the kinetic energy does. A basketball bounces, yet each bounce is a little lower and makes a sound: some kinetic energy transforms at every bounce, so each bounce is an inelastic collision.
Only a collision that keeps the system's total kinetic energy unchanged is elastic. Every collision that transforms some of it is inelastic.
Two curling stones collide and glide apart, with the system's total kinetic energy very nearly unchanged. To a good approximation, is the collision elastic or inelastic?
Two cars collide and their fenders crumple; the impact makes a loud bang. Classify the collision as elastic or inelastic.
The crumpled fenders are deformation, and the bang is sound.
Both came from the system's kinetic energy, so some kinetic energy transformed into other forms.
A collision that transforms some kinetic energy into heat, sound, or deformation is inelastic.
The collision is inelastic.
Lando says: a collision can be inelastic even when the objects bounce apart, because what decides the class is whether some kinetic energy transformed into forms such as heat or sound. Is he correct?
Which statement describes an inelastic collision?
Which of these collisions is elastic, to a good approximation?
A table-tennis ball bounces on a table; each bounce is a little lower than the one before and makes a click. Which statement about the bounces is correct?