Ablock of mass m = 3 kg is held against a wall with a force f applied at an angle φ, as shown. there is a coefficient of static friction μs = 0.25 between the block and the wall. if φ = 60°, then the minimum f required to hold the block up is

Electric field of the earth. the earth has a net electric charge that causes a field at points near its surface equal to 150 n> c and directed in toward the center of the earth. (a) what magnitude and sign of charge would a 60-kg human have to acquire to overcome his or her weight by the force exerted by the earth’s electric field? (b) what would be the force of repulsion between two people each with the charge calculated in part (a) and separated by a distance of 100 m? is use of the earth’s electric field a feasible means of flight? why or why not?