The acceleration due to gravity at the surface of a planet depends on the planet's mass and size; therefore other planets will have accelerations due to gravity different from 9.8 m/s2. imagine an astronaut stands on an alien planet, which has no atmosphere, and throws a rock with a speed of 7.45 m/s in the horizontal direction, releasing it at a height of 1.40 m above the surface of the planet. the rock hits the surface a horizontal distance of 8.90 m from the astronaut. find the magnitude of the acceleration due to gravity on this alien planet.