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Free Fall question ?

A tennis ball is thrown vertically upward with an initial velocity of +8.0 m/s.  What will be the ball's speed when it returns to it's starting position ?

I solved this using motion equations and got +/- 8.0 m/s for the answer.  The book says answer is 8.0 m/s.  I believe the answer is   - 8.0 m/s.   Am I correct ?
1 Solution
Your are correct it arrives back with the same speed in the other direction, ie velocity -8m/s.

I'd be careful how they are defining speed though, an argument could be made that the speed is 8m/s. But I doubt at this level they are doing this. Speed and velocity are not quite the same thing, velocity has a directional component to it.
velocity is a vector .
if you define the upward velocity as positive then the end velocity would be negative.

i.e. the velocity  at the end is going in the opposite direction to the initial velocity so
you could say its negative relative to the starting velocity.
but its all relative

but actually the question talks about speed which is a scalar so it doesn;t have direction
speed is positive or zero, so book is right (if they are asking for speed and not velocity).
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