S11.2 momentum theoremTake y, the vertical axis of lead, as positive upward.Accordingto the momentum theorem:mv, -mv, = pSo, we know that v, = O , after (T+ t) seconds, p = O . There arep = Nt -Q(T +t) = 02H二+）N = O(hence,g2 ×1.5N = 300+1= 16.9KN0.0119.8
Take y, the vertical axis of lead, as positive upward. According to the momentum theorem: mv2 − mv1 = p So, we know that , after (T+ 0 t) seconds, . There are v1 = p = 0 p = Nt − Q(T + t) = 0 hence, = + = +1 1 2 ( 1) g H t Q t T N Q N 1 16.9KN 9.8 2 1.5 0.01 1 300 = + = §11.2 momentum theorem
$11.2 momentumtheorem2. Momentum theorem of particle systemFora single particle,the momentumtheorem is:d(m,v)= F(e) -+)dtThe momentum theoremoftheparticle system isdZ(mv) =ZF(e)+EFOdtdpDifferentialequation ofmomentumZF(e)theoremforparticle systemdtThat is, the derivative of momentum with respect to time ofthe system of particles isequal to the vector sum of the external forces on the system of particles
2. Momentum theorem of particle system §11.2 momentum theorem ( ) ( ) ( ) e i i i i i d m v F F dt = + For a single particle, the momentum theorem is: ( ) ( ) ( ) e i i i i i d m v F F dt = + The momentum theorem of the particle system is: (e) i dP F dt = Differential equation of momentum theorem for particle system That is, the derivative of momentum with respect to time of the system of particles is equal to the vector sum of the external forces on the system of particles