How to determine velocity from speed? *edit?

I got in a brief argument yesterday jumped the gun and said "Acceleration = Change in speed/ time in which it occurred" Now today because is said "speed" Not velocity I'm losing the argument. What I need is What information is required (besides objects speed and direction) is required to... show more I got in a brief argument yesterday jumped the gun and said "Acceleration = Change in speed/ time in which it occurred"
Now today because is said "speed" Not velocity I'm losing the argument. What I need is
What information is required (besides objects speed and direction) is required to calculate velocity and in turn calculate acceleration.
Assuming all variables are obtainable is velocity just speed and direction? Just assuming its an object in motion what would I need to know about that object to calculate velocity. And say it was changing directions what effect on velocity would that have?
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