What makes some collisions elastic and others inelastic?

If the collision involves bouncing, it is elastic.

If the collision involves sticking together, it is elastic.

If there is no loss of kinetic energy in the collision, it is inelastic.

If there is energy lost in the collision to sound, heat, etc., the collision is inelastic.

Consider a 1000 w iron whose base plate is made of 0.5 cm thick aluminum alloy 2024-t6 (ρ = 2770 kg/m3 and cp = 875 j/kg°c). the base plate has a surface area of 0.03 m2. initially, the iron is in thermal equilibrium with the ambient air at 22°c. assuming 90% of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 200°c.