In a one-dimensional elastic collision a ball of mass 0.51 kg, moving with velocity 6.4 m/s, strikes an initially stationary ball of mass 0.89 kg. Find the final velocity of the initially moving ball.

Asmall object with mass 0.200 kg swings back and forth on the lower end of a light rope that is 3.00 m long. the upper end of the rope is attached to the ceiling. as the object swings through its lowest position, where the rope is vertical, the speed of the object is 5.80 m/s. at this point in the motion, what is the tension in the rope? (use g = 9.80 m/s2.)