Here is my question: A stone is thrown straight up with a speed of 15.0 m/s. How fast will it be moving when its altitude is 8.0 m above the point from which it was thrown? How much time elapses while the stone is reaching that height? (Is there one answer or are there two answers? Why?) --- I know that the stone goes up and then down again, so there could be two answers, but how exactly would I solve this problem?