Question is from Barron's SAT subject test Physics
"A flat railroad car is moving to the right at 5m/s. A person standing on the car throws a ball straight upward at 20m/s. If air resistance is negligible, where will the ball be in relation to the person's new position at the time when the ball returns to its original starting height?"
The answer is C) the ball will land in the person hand. The book explains that before throwing the ball vertically, the ball and the person have a horizontal velocity of 5m/s. I don't get this bit, if we intentionally throw the ball vertically, how can it get horizontal velocity? I initially answered E)"The ball will land 20 m behind the person"