A student standing on the edge of a 78m-high cliff throws a rock straight downward with an initial speed of 4.0m/s. Assume air resistance is negligible and take the magnitude of the acceleration due to gravity to be 10m/s2.
(a) Determine the time it takes for the rock to reach the ground below the cliff. Show all algebraic steps leading to your solution.
(b) Calculate the rock’s speed immediately before it strikes the ground. Provide your answer with units and explain how you obtained it.