Your horizontal motion has no effect on the answers. Your sister is standing on the sidewalk as you skate by. At the same exact instant that you toss yours, she tosses another baseball straight up at 25 m/s, and she gets exactly the same answers as you get.
The acceleration of gravity is 9.8 m/s² down, so each baseball loses 9.8 m/s of upward speed each second after you toss them. They can only continue going up for (25/9.8) = 2.55 seconds. At that point, each ball has run out of upward gas, stops, turns around, and starts falling. It takes the same 2.55 seconds to return to the same height from which it was tossed. So each ball takes (2 x 2.55) = 5.1 seconds to land back in your hands.
The average speed of each ball on the way up is
(1/2) (speed at the bottom + speed at the top)
= (1/2) (25 + 0) = 12.5 m/s ,
and it spends 2.55 seconds rising.
The distance it covers upward is
(average speed) x (time)
= (12.5 m/s) x (2.55 sec)
= 31.875 meters .
There it is. The physics and math are bullet-proof, but the numbers are whacko.
From a skateboard, you tossed a baseball straight up at 56 miles per hour ... fast enough for it to reach 105 feet, possibly the height of a 7-story building, before it falls back !
