A40-kg mass rest at the edge of a board that is 2 meters long. the coefficients of friction are .80 and .40. the board is slowly raised until the mass just begins to slide. at what angle does the mass begin to slide?

Plss anybody know how to do this? ? i need the answers from a through d

What are similarities and differences of reflection, refraction, diffraction and absorption?

In a set amount of time, a battery supplies 25j of energy to an electric circuit that includes two different loads. one of the loads produces 10 j of heat energy during this time interval. how much heat energy is produced by the second load in this time? explain your answer