4.4 Differential Equation of linear momentum Newton’ s second law F=ma=pdxdydz Rodxdvdz Elemental volume =(Xi+yj+Zk)pdxdydz What are the surface forces Fs on the elemental volume?11 Newton’s second law dV dxdydz dt =   b s dV dxdydz F F dt   = + F R dxdydz b =  = + + ( ) Xi Yj Zk dxdydz  4.4 Differential Equation of Linear Momentum dx dz dy Elemental volume F ma = What are the surface forces Fs on the elemental volume?