How do you calculate initial speed?

Answer 1

Many, many, many, many different ways.

o = initial

First option: v=vo+at

Second option: v^2=vo^2+2a(x-xo)

Third option: y=yo+vot+(1/2)at^2

Fourth option: y=(v^2-vo^2)/(2a)

etc...

However, you will have to use your basic algebraic skills to isolate initial velocity.