How can assumptions impact the calculation of projectile and explosion?

[amcavoy]

A shell is fired from a gun with a muzzle velocity of 600 m/s at an angle of 30.0^o with the horizontal. The shell explodes into two fragments of equal mass 41.0 s after leaving the gun. Fragment A, whose speed immediately after the explosion is zero, falls vertically. Fragment B proceeds in the forward direction. How far from the gun does fragment B land? What additional assumptions are needed to answer this question?:

1. energy is conserved
2. Instantaneous explosion
3. No air resistance
4. Level terrain
5. Flat earth
6. Constant g

I got the answer to the first part (35,374.04 m), but I'm having trouble with the second. At first, I thought 1,2,3,6 would be the answer, but that was wrong. Then, I said that 2,3,6 would be the answer, but that too was wrong. Now I am thinking that the energy wouldn't matter (momentum, however, would matter). 2 definitely needs to be assumed, as well as 3,4,5, and 6. The answer would change if there was air resistance, the terrain wasn't level (which would in turn that the Earth isn't flat), and finally if g was taken to be universal gravity rather than local, the answer would change a bit. Would I be correct to assume 2,3,4,5,6?

Thank you.

 

[amcavoy]

This question is sort of vague. 4 and 5 would basically be the same (at least in this context).

 

[daniel_i_l]

If 4 and 5 are the same then your answer is correct.
In an explosion energy isn't conserved cause of the explosion, when you trigger the explosion then you change the energy:
if there is a bomb at rest then its energy is 0. But when it explodes it has a lot of kinetic energy.