A board of uniform size and composition sits horizontally on support positioned under its center. The mass of the board is unknown.
If there is a 20 kg mass is on the right-hand end of the board what is the constant of the spring holding the other end f of the board if it is stretched 0.50 m past its equilibrium position?

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.