A charged metal sphere is hung vertically from a silk string. If another metal sphere with an identical charge is brought nearby, how will the first sphere move? A.
The first sphere will move toward the second sphere.
B.
The first sphere will not move.
C.
The first sphere will move away from the second sphere.
D.
The first sphere will orbit the second sphere.

it is a negative acceleration

not too sure thinking all accelerations are pointed down

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =