The number of neutrons in an atom affects the atomic of the atom

mass?

Yes. They affect the atomic mass. We know, 

Atomic mass = Number of Protons + Number of Neutrons.

So, they contribute in atomic mass.

Hope this helps!

Ithink the answer would be 1,350!

The objects do not reach terminal velocity         there is not enough time from the time the object falls from when it hits the ground to achieve terminal velocity. an object must be placed higher to achieve terminal velocity in order to be in free fall.