Find the mass of a ball on a roof 30 meters high, if the ball's gravitational potential energy is 58.8 joules

The potential energy of an object is calculated by the expression:

PE = mgh    where m is the mass, g is the gravitational acceleration and h is the height of the object from the ground.

PE = 58.8 J = m (9.81 m/s^2) (30 m)

m = 0.1998 kg

Hope this helps.

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.