One dimensional motion: quiz 2

Chef Susan tosses some pizza dough in the air, then catches it again at the same height. The pizza dough is in the air for  . We can ignore air resistance.

What was the dough's velocity at the moment it was tossed into the air?

Answer using a coordinate system where upward is positive.

Round the answer to two significant digits.

 

Answer:

Let's list all the variables. Remember, upward is the positive direction.

 

A= -9.81m/s^2

T= 1s

Displacement= 0m

Vf= ?

Vo= ?

 

How do I know that the displacement equals to 0, when displacement is not given?