Concept Simulation $2\mathrm{.}3$ offers a useful review of the concepts central to this problem. An astronaut on a distant planet wants to determine its acceleration due to gravity. The astronaut throws a rock straight up with a velocity of $+10\mathrm{.}1$ m$/$s and measures a time of $20\mathrm{.}4$ s before the rock returns to his hand. What is the acceleration $($magnitude and direction$)$ due to gravity on this planet? $($positive $=$ up$,$ negative $=$ down$)$