An astronaut on a newly discovered planet wants to determine the acceleration due to gravity. In his experiment, he fires a small cannon from the edge of a mesa that is 125m high. The initial horizontal velocity of the cannon ball is 64m/s. The projectile travels 261m horizontally before it strikes the surface of the planet. After determining the acceleration due to gravity, what might the astronaut conclude about this planet? answer: Ag=15.03m/s^2 i don't get it at all, help please, and thanks!