Answer:
The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10−34 when expressed in the unit J⋅s, which is equal to kg⋅m2⋅s−1, where the metre and the second are defined in terms of c and ΔνCs.
Aware is 3(A) I hope this helps
Answer:

Explanation:
Given
charge on the fixed particle, 
mass of the second charge, 
distance between the fixed charge and the floating charge on the top, 
- According to the question the second charge is floating just above the fixed positive charge despite of gravity this means that the floating charge is also positive in nature and hence feels the repulsion from the fixed charge which is equal in magnitude to the gravitational force on the charge.
where:
permittivity of free space
g = acceleration due to gravity

