Elastic
☑ occur when the colliding objects bounce off of each other
☑ hard or bouncy objects
☑ kinetic energy is conserved
Inelastic
☑ occur when two objects collide
☑ two objects colliding stick together
☑ kinetic energy is not conserved — some of the initial kinetic energy is converted into other types of energy (heat, sound, etc.)
Answer:
If the light were incident upon two polarizers at right angles, no light would get thru - thus each polarizer must block 50% of the light.
One polarizer would allow 50% of the light to pass.