A clay ball with a mass of 45 g is attached to a long string to make a pendulum. The ball is pulled back so that the string is horizontal to the ground, and is then released. At the bottom of the ball's path is another clay ball that has a mass of 75 g and is at rest. The two balls collide in­elastically, so that they follow the path of the first ball beyond the point of collision. What must the speed of the first ball be just before the col­lision so that the combined balls rise to a height of 8.0 cm above the