物理与光电工程学院：《大学物理》课程PPT教学课件（讲稿，英文第三版）Chapter 9 Momentum and The Conservation of Momentum

Chapter 9 Linear Momentum and Chapter 9 Momentum and the conservation of Momentum 1. Linear Impulse and Momentum 2. Impulse-Momentum Theorem and Conservation of Momentum

Chapter 9 Linear Momentum and Collisions Chapter 9 Momentum and The Conservation of Momentum 1. Linear Impulse and Momentum 2. Impulse-Momentum Theorem and Conservation of Momentum

Chapter 9 Linear Momentum and New Words Impulse 冲量 Momentum 动量 Impulse and linear momentum theorem Collisions 碰撞

Chapter 9 Linear Momentum and Collisions New Words Impulse 冲量 Momentum 动量 Impulse and linear momentum theorem Collisions 碰撞

Chapter 9 Linear Momentum and 9-1 Momentum and Its relation to Force P200-201 1. momentum(动量) Momentum of an object is defined as the product of its mass and its velocity Momentum is presented by the symbol p 动量 p= no

Chapter 9 Linear Momentum and Collisions 9-1 Momentum and Its Relation to Force P200-201 1. momentum（动量） Momentum of an object is defined as the product of its mass and its velocity. Momentum is presented by the symbol P .  动量 v   p = m

Chapter 9 Linear Momentum and 2 Newton second law of motion in terms of momentum ip dt m is a constant, Sof= dp d(my) dt dt F d For a particle net net,s

Chapter 9 Linear Momentum and Collisions 2 Newton second law of motion in terms of momentum m is a constant， so： dt dP Fnet   = Fnet = ma  For a particle t p F d d   = ma t m t p F     = = = d d( d d v)

Chapter 9 Linear Momentum and 9-2 Conservation of linear momentun(动量守恒 p202-205) In equation: FY dP net dt Let F=0 net P=constant vector 动量守恒定律 若质点系所受的合外力为零F=∑F=0 则系统的总动量守恒,即P=∑保持不变

Chapter 9 Linear Momentum and Collisions 9-2 Conservation of linear momentum（动量守恒 p202-205） dt dP Fnet   In equation: = Let Fnet = 0  P = constant vector 若质点系所受的合外力为零 则系统的总动量守恒，即 保持不变 . 0 ex ex =  = i F Fi   =  i p pi   动量守恒定律

Chapter 9 Linear Momentum and If no net external force acts on a system of particles, the total linear momentum of the system cannot change Discussion 1)守恒条件合外力为零F=∑F=0 当F<<F时,可略去外力的作用,近似地 认为系统动量守恒.例如在碰撞,打击,爆炸等问题中

Chapter 9 Linear Momentum and Collisions If no net external force acts on a system of particles, the total linear momentum of the system cannot change. Discussion 1）守恒条件 合外力为零 当 时，可 略去外力的作用, 近似地 认为系统动量守恒 . 例如在碰撞, 打击, 爆炸等问题中. 0 ex ex =  = i F Fi   ex in F F   

Chapter 9 Linear Momentum and 2)若某一方向合外力为零,则此方向动量守恒 Fe=0 ∑ F=0,P, FEx=O ,=C 2 12 If the component of the net external force on a closed system is zero along an axis then the component of the linear momentum of the system along that axis cannot change

Chapter 9 Linear Momentum and Collisions If the component of the net external force on a closed system is zero along an axis, then the component of the linear momentum of the system along that axis cannot change. 2）若某一方向合外力为零, 则此方向动量守恒 . z z i i z z y y i i y y x x i i x x F p m C F p m C F p m C = = = = = = = = =    v v v 0, 0, 0, ex ex ex

Chapter 9 Linear Momentum and 93 collisions(碰撞) and Impulse(冲量) 1. Collision Collisions: in a collision, two bodies exert strong forces on each other for a relatively short time. This forces are internal to the two-body system and are significantly larger than any external force during the collision

Chapter 9 Linear Momentum and Collisions 9-3 collisions (碰撞) and Impulse (冲量) Collisions: in a collision, two bodies exert strong forces on each other for a relatively short time. 1. Collision This forces are internal to the two-body system and are significantly larger than any external force during the collision

Chapter 9 Linear Momentum and 2 The impulse(冲量) 力的累积效应 F(O)对t积累→>p,Ⅰ F对F积累→)W,E dp d(mu dt It =dp=d (mv) Fdt= p2-p1=mo 2-120 Fat The impulse(冲量) of force ◆冲量力对时间的积分(矢量)7=2Fdt

Chapter 9 Linear Momentum and Collisions 2 The impulse (冲量) 力的累积效应 F r W E F t t p I , ( ) , → →      对 积累 对 积累 2 1 2 1 2 1 d v v      F t p p m m t t = − = −  t m t p F d d( d d v)    = = d d d ( v)    F t = p = m 冲量 力对时间的积分（矢量）  = 2 1 d t t J F t   —– The impulse(冲量)of force  = f i t t J Fdt  

Chapter 9 Linear Momentum and 3 Momentum Theorem 研究力和运动的时间积累过程关系 Fd=2-=m2-m 动量定理在给定的时间内,外力作用在质点 上的冲量,等于质点在此时间内动量的增量 Net linear impulse delivered to a particle equals the change in linear momentum of the particle

Chapter 9 Linear Momentum and Collisions 3 Momentum Theorem 研究力和运动的时间积累过程关系. 动量定理 在给定的时间内，外力作用在质点 上的冲量，等于质点在此时间内动量的增量 . 2 1 2 1 2 1 d v v      F t p p m m t t = − = −  Net linear impulse delivered to a particle equals the change in linear momentum of the particle