An object on another planet with g = 25 m/s^2 hits the ground from rest in 4 seconds. How far did it fall? Choices:
•200.0m
•100.0m
•1000.0m
•25.0m

Using the kinematics equations Vf=Vi+ (a)(t) and d=Vi(t)+1/2(a)(t)^2
and given:

d=?
Vi= 0 m/s
Vf=?
g= 25m/s^2 (so a= 25m/s^2)
t= 4sec

you first have to use Vf=Vi+ (a)(t) to solve for Vf:

Vf= (0m/s) + (25m/s^2)(4 sec)
Vf= 100m/s

Now using d=Vi(t)+1/2(a)(t)^2

d= 0m/s +1/2(25m/s^2)(4)^2

Which gives us d= 200.0 meters

Letter a, because when there are unlike charges they will always attract to each other.