Chapter 9, Problem 81P

A 14-kg projectile is launched at 380 m/s at a 55° angle to the horizontal. At the peak of its trajectory it collides with a second projectile moving horizontally, in the opposite direction, at 140 m/s. The two stick together and land 9.6 km horizontally down-range from the first projectile’s launch point. Find the mass of the second projectile.