I don't understand how to solve those problems. I need help.

1. A 12 k3 object sits on a horizontal surface. If the [1 between the object and the surface is 0.086,. how much force is needed to give the object an acceleration of 4.5 mfs'? 2. In order to push a 20 kg block of wood up a 22" ramp. a force of 200 N is needed (assume constant velocity). What is the it between the block and the ramp? 3. A 100 kg person skis down a mountain with an acceleration of 1.6 mfs'. If the mountain has an angle of 28". calculate the following: A} The net force that accelerates the skier B) The force of friction C) The coefficient of friction (l1)