Solving a Physics Problem: Cannon Shell Split and Momentum Calculation

[zinedine_88]

here is the problem.

A cannon shoots a 6 lb shell straight up. It reaches its maximum height, 1024 feet, and splits into two pieces, 2 lb and 4 lb. The two pieces are observed to strike the ground simultaneously. The 4 lb piece hits the ground 1600 feet away from the explosion(measured along the x AXIS)

a. How long would it have taken the shell to return to the ground if it had not split?

I found the TIME=8 seconds.

b.Find the velocity of each of the two pieces just after the explosion.

2lb piece - 400 ft/s
4lb piece - 200ft/s

AND PART "C" is where I get stuck! PLEASE HELP HERE.
Here is part "C"

c. Find the momentum of each piece just before they strike the ground.WHAT SHOULD I DO.
Please Help

The answer in the book is
2lb piece - p(vector) = -25i(unit vector)x - 16i(unit vector)z
4lb piece - p(vector) = 25i(unit vector)x - 32i(unit vector)z

 

[zinedine_88]

I know its something easy but i just can't get it :(

 

[Vidatu]

Unless there's something I'm missing, you should be able to just use p=mv.

Just make sure to use velocity at the instant of interest, not immediately after separation.

 

[zinedine_88]

I tried, but I don't know what to use for my initial momentum and my final momentum.

It is just so weird looking... I mean.. the velocity is Vx +Vy but.. the numbers are too big to get such a numbers.

i have no clue...

 

[jdogg0075]

If I am not mistaken it dosent matter what mass something is. A 6lb. weight will hit the ground the same time as a 4lb and a 2lb as long as they are at the same height. And from what you said they spit at their max height.