Quote:
Originally Posted by Shownomercy
Drivers BAC lol. But even then, wouldn't the ball still have negative velocity? Assuming the truck is positive velocity and yes I know, can't be negative but you get what I am saying. The ball would have zero relative velocity to an on looker but wouldn't it still accelerate?
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Velocity can be negative it would mean that the ball is slowing down. You can relate positive and negative with direction of forces, (foreword = positive, backwards = negative) but that doesnt have much to do with the question. When a change in velocity occurs there is a change in acceleration.
I'm not sure exactly what you mean but I think it's this. In the original question the ball is traveling with the truck at 55mph and it positively accelerates to reach a velocity of 55mph traveling away from the line.
In the case where the truck stopped on the line and the ball is fired the ball has no velocity but is acceleration in opposition with the truck which is why it goes no where.