A sled and rider have a total mass M. They are at rest on a snowy hill. The coefficient of static friction between the sled and the snow is s. Find an expression for the maximum angle of the hill's slope measured upward from the horizontal in terms of s. (Use the following as necessary: s and M.)

Two cannon balls weighing 18 kg and 24 kg are chained together and fired horizontally with a velocity of 165 m/s from the top of a 21-m wall. the chain breaks during the flight of the cannonballs and the 18-kg cannonball strikes the ground at t = 1.5 s, at a distance of 240 m from the foot of the wall, and 7 m to the right of the line of fire. determine the position of the other cannonball at that instant. neglect the resistance of the air.