A ball traveling 20 m/s strikes a wall and rebounds in the opposite direction at 18 m/s. If the collision with the wall took 0.2 s, what was the average acceleration of the ball? 2 m/s2
190 m/s2
38 m/s2
10 m/s2

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.)