A spring with a force constant of 5.0 N/m has a relaxed length of 2.59 m. When a mass is attached to the end of the spring and allowed to come to rest, the vertical length of the spring is 3.86 m. Calculate the elastic potential energy stored in the spring. Answer in units of J.

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.