Three blocks were placed on a massless rod. Red block has a mass of 8kg and is placed 7m right of the green block (9kg). The blue block (12kg) is 3m left of the green block. Find the center of mass of this three block system.

answer is c

explanation:

the answer would be   dignified - apex

d) physical means can be used to separate the components of air.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.