If you drop a rock from a height of 10 m , it ac- celerates at g and strikes the ground 1.42857 s later. If you drop the same rock from half that

If you drop a rock from a height of 10 m , it ac- celerates at g and strikes the ground 1.42857 s later. If you drop the same rock from half that height, what will be its acceleration? The acceleration of gravity is 9.8 m/s 2 .