To solve this kinematics formula use the following equation:
Vf = Vi + at
Vf = 0 + (9.81 m/s^2)(3 seconds)
Vf = 29.43 m/s and or about 29.4 m/s of reported to 3 significant figures.
Your question is inappropriate and unclear to read it. It doesn't make any sense.
What are the answer choices???
A) Mass Number
B) Protons and Electrons
C) (I think group but I'm not 100% sure on this...)
D) 12 (To work out the number of neutrons you do MASS number - ATOMIC number aka the number of protons so in this case you'd do 23-11=12)
Hope this helps