Collisions

• Two classifications - Elastic and Inelastic

Elastic

• Total Kinetic Energy ($TKE$) of an object in motion is conserved

Inelastic

• Total Kinetic Energy ($TKE$) of an object in motion is not conserved
  • Some of it is transformed into other types of energy e.g heat, sound and light

Example Questions

• A bear of $24.2kg$ is travelling east at $6.66m\space s^{-1}$ when it collides with something sticky and disgusting which has mass $8.47kg$ and is travelling west at $7.77m\space s^{-1}$. They coalesce to form a sticky, disgusting bear mass thing (sdbmt).
  • What is the final velocity of the sdbmt?
    • $6.95m s^{-1}$
  • Show by calculation whether the collision was elastic or inelastic. Justify your answer.
    • It is inelastic. To prove, $TKE_{1} \not= TKE_2$
    • $TKE_1=\frac{1}{2}24.2\times 6.66^2=536$
    • $TKE_2=\frac{1}{2}8.47 \times (-7.77)^2$