a stone is thrown vertically upward with a speed of 20m/s from the top of a building 35m high. What would be the speed of the stone when it reaches a point 12m above the ground (g=9.8)

When a vertical beam of light passes through a transparent medium, the rate at which its intensity i decreases is proportional to i(t), where t represents the thickness of the medium (in feet). in clear seawater, the intensity 3 feet below the surface is 25% of the initial intensity i0 of the incident beam. what is the intensity of the beam "10" feet below the surface? (give your answer in terms of i0. round any constants or coefficients to five decimal places.)