Just as the last passenger steps out of the elevator at the thirteenth floor, a malfunction occurs and it begins dropping toward the ground floor in free fall, Ignoring friction (and the fact that elevators are designed to avoid this type of accident), what is its downward acceleration? How fast is it moving after 2.5 s?

It may possibly be c i think |-/

The rocks expand when there hot/warm  and contract when they are cold.

How is it possible that phylogenies based on sequences from nuclear genomes and organellar genomes (i.e., chloroplasts and mitochondria) from the same group of species yield phylogenetic trees with different branching orders?   answer :   the genome of the endosymbiont is more closely related to members of the group in which it originally evolved, while the nuclear genome of the engulfing organism has its own evolutionary trajectory.