a projectile of mass 3 kg is fired at 120 m/s at an angle of 30 deg. at the top of the trajectory the projectile explodes into 1 kg and 2 kg fragments. the 2 kg fragment lands directly below the point of explosion. it takes 3.6 sec for the 2 kg object to reach earth. find the distance between the point of firing and the point at which the 1 kg object strikes the ground. Ive figured out where the 2 kg object lands to be 634 meters from the point of firing. The top of the trajectory is 184 meters up. When the object explodes the 2 kg object takes some of the KE because it only takes 3.6 sec to reach the ground. So using conservation of energy i set up an equation like this 1/2(3kg)(v^2) = 1/2(2kg)(33.5^2) + 1/2(1 kg ) v1^2. I'm trying to find v1 so i can find the distance. but i dont know what to use for v. do i use the 120 m/s or do i use the horizontal component of the velocity which is 104 m/s?