The answer is the first one
Answer:
Explanation:
Given
acceleration of system a =1.2 m/s^2
Normal Force N=4.45 N
Force exerted F=20 N
Thus


-------1
Normal reaction 


therefore 

Answer:
The charge at the center of the conducting sphere is zero.
Explanation:
A principle of conductor materials is that the electric field inside a conductor in electrostatic state is always zero. The gauss law says that the flux of a electric field in a closed surface is proportional to the charge enclosed by the surface. Then if the Electric field inside of a conductor is zero, imperatively the charge anywhere inside the conductor is zero too, so the charge at the center of the sphere is zero.