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Is final velocity a vector or scalar?

A ball starts from rest at point A and rolls .9 meters east to point B with an average velocity of 2 m/s. What was the velocity of the ball at B?
Given:
Vi=0 m/s 
d (displacement)= .9m east
average velocity= 2 m/s 
Vf= ???
 
average velocity = Vf + Vi divided by 2
 
is the answer 4 m/s or 4 m/s East? 
Does the answer for final velocity include direction or no?
                            
 
 
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1 Answer

vi = 0  (started from rest)
 
<v> = average velocity = 2 m/s  (given)
 
<v> = (vi + vf)/2 ⇒ 
 
vf = 2<v> - vi = 2(2 m/s) - 0 = 4 m/s
 
Velocity is a vector, so the complete answer must have both a magnitude and direction.  Therefore
 
vf = 4 m/s east
 
or
 
vf = (4 m/s)i  (if you are familiar with the i, jk notation).