The initial energy is equal to zero because the starting point is set at zero height to make things easier.

regarding the law, the 15th amendment was specifically designed thinking in the rights of black free men.

even though ratified on february 3, 1870, the promise of the 15th amendment would not be fully applied for a long time.poll taxes and literacy tests would allow southern states disenfranchise african americans. only in 1965 the voting rights for african americans would be actually able to vote in the south.

in 1965, president johnson signed the voting rights act, which aimed to overcome legal barriers that prevented african americans from voting as it was guaranteed by the 15th amendment to the u.s. constitution.

a u.s. citizen has to have lived in and been an american citizen for a year or more be for he or she can vote for presidential or country wide elections. they also have to register to vote. if the voting is for state representatives or issues, they have to have lived in that state for one month or more and meet the requirements for country wide elections.