# Center of mass after explosion [closed] How he treated the center of mass as if it is still in the same place , is not it supposed to change after explosion ? and is not explosion destroying the closed system? i mean it represents and external force and energy , so how can i use conservation laws ?

• related (duplicate?): physics.stackexchange.com/q/135208 – Kyle Oman Oct 14 '14 at 21:39
• maybe the part of explosion but i can not understand the motion of center of mass after explosion so i posted these Question – Mohamed Osama Oct 14 '14 at 21:41
• Unless there is an external force acting on the system, the speed of the center of mass will not change. That's a fundamental property of closed systems that follows directly from Newton's laws. So if it was moving at 150 m/s before the explosion, it is still moving at 150 m/s after the explosion - conservation of momentum demands it. – Floris Oct 14 '14 at 22:55

In the X-Dir: $p_x = m_Av_{xA} + m_Bv_{xB} + m_Cv_{xC} = 100*555/2.5+60*255/2.5+40*105/2.5 = 30000Ns$
In the Y-Dir: $p_y = m_Av_{yA} + m_Bv_{yB} + m_Cv_{yC} = 100*-180/2.5+60*0/2.5+40*450/2.5 = 0Ns$
In the Y-Dir: $p_z = m_Av_{zA} + m_Bv_{zB} + m_Cv_{zC} = 100*240/2.5+60*-120/2.5+40*-420/2.5 = 0Ns$