Tham khảo tài liệu 'crc press - mechanical engineering handbook- mechanics of solids part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 1-40 Section 1 H H i H j H k O x yj z Hx m yvz - zvy H m zv - _vv y x Hz m xvy yvx Time Rate of Change of Angular Momentum In general a force acting on a particle changes its angular momentum the time rate of change of angular momentum of a particle is equal to the sum of the moments of the forces acting on the particle. Vectors HO d r X mv rx F HO Scalars Y M H Y M H Y M H x x y y z z M 0 H r X mv constant O O conservation of angular momentum A special case is when the sum of the moments about point O is zero. This is the conservation of angular momentum. In this case motion under a central force if the distance r increases the velocity must decrease and vice versa. Impulse and Momentum Impulse and momentum are important in considering the motion of particles in impact. The linear impulse and momentum equation is ih F dt mv2 t ft impulse momentum mv1 t initial momentum Conservation of Total Momentum of Particles Conservation of total momentum occurs when the initial momentum of n particles is equal to the final momentum of those same n particles n n Y mv 1 Y mv 2 i i total initial total final momentum at time t1 momentum at time t2 When considering the response of two deformable bodies to direct central impact the coefficient of restitution is used. This coefficient e relates the initial velocities of the particles to the final velocities vBf vAf relative velocity of separation vA vB relative velocity of approach
