What is 1+2 plz answer

Which describe reflection? check all that apply. light bounces off a boundary.

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.

Specific heat refers to the amount of heat required to change 1 gram of a substance by degree(s) celsius