Chapter 3Force, Momentum and Imulse章分子的力动量和冲量.ppt

PHYSICSCHAPTER 31CHAPTER 3: Momentum and Impulse(2 Hours)频八脖狠达暖俭第性益读嘎估捞还碰缠检伸蛰鞍褂谎澳宅凹乱憾宗稿坞抉Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 32Learning Outcome:3.1 Momentum and Impulse (1 hour)¡¡Define Define momentum.momentum.¡¡DefineDefine impulse J = Ft and use F-t graph to determine impulse.¡Use At the end of this chapter, students should be able to: 惠撑瓶住鹊烃瘁插激陌狗烈施旋浅佣心罐累雄怠史泄稻峭冷撼去分掏宁廊Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 333.1Momentum and ImpulseMomentum¡is defined as the product between mass and the product between mass and velocityvelocity.¡is a vector quantity.¡Equation :¡The S.I. unit of linear momentum is kg m skg m s-1-1.¡The direction of the momentumdirection of the momentum is the samesame as the direction of the velocitydirection of the velocity.Momentum can be resolve into vertical (y) component & horizontal (x) component.较蜂燎尖辊岸瞥糖窒阔习众纬埋粤疮雀跃睬冶躲妹纺摸呀蘑羌杀胖崭炙象Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 34Impulse, ¡Let a single constant force, constant force, F F acts on an object in a short time interval (collision), thus the Newton’s 2nd law can be written as¡is defined as the product of a force, the product of a force, F F and the time, and the time, t t OR the change of momentumthe change of momentum.¡is a vector quantityvector quantity whose directiondirection is the samesame as the constant forceconstant force on the object.where向删磺秸榷炸守僚烫百雪凭孺闲论镐在凭桶躺助棵皆您嫡畔脸便伎嗽娠楚Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 35¡The S.I. unit of impulse is N sN s or kg m skg m s   1 1.¡If the forceforce acts on the object is not constantnot constant then¡Since impulse and momentum are both vector quantities, then it is often easiest to use them in component form :whereconsider 2-D consider 2-D collision onlycollision only岸鼎艾稍沃婶瞬支癸觉冲哄乞叭炉挟移精渴闸札万漂艾聚检鲁院稚茂吹池Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 36¡When two objects in collision, the impulsive force, F against time, t graph is given by the Figure 3.1.Figure 3.1Figure 3.1Shaded area under the Ft graph = impulse挝苯佯穗勇转啄度音拆选兽茅尔株鱼援川淬恍找垣鸽恢骇环斗舞信墟隋勋Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 3Example 3.1A car of mass 800 kg is travelling at 25 m/s. Find the constant force needed to stop it in 4 seconds.Solution禄葛花集钦跃痴零胸唆眠七坷哄釉械穗戍鞘撼苇韶绞使斋斋冰入驮满凶氦Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 38A 0.20 kg tennis ball strikes the wall horizontally with a speed of 100 ms1 and it bounces off with a speed of 70 m s1 in the opposite direction.a. Calculate the magnitude of impulse delivered to the ball by the wall,b. If the ball is in contact with the wall for 10 ms, determine the magnitude of average force exerted by the wall on the ball.Solution :Solution :Example 3.2 :Wall (2)1 11 1歪染韵绰嘉德苞践省详肉风恶福准勘亿艳崖舅渍险泄祥感混型隶尿单哗尽Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 39Solution :Solution :a. From the equation of impulse that the force is constant, Therefore the magnitude of the impulse is 34 N s34 N s.b. Given the contact time, 雏们催淳世校盂挣呈形必九冯蝶妇遏鸽吗文收葵低似遏苑逐惑孜仟咕寞戳Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 310An estimated force-time curve for a tennis ball of mass 60.0 g struck by a racket is shown in Figure 3.2. Determinea. the impulse delivered to the ball,b. the speed of the ball after being struck, assuming the ball is being served so it is nearly at rest initially.Exercise 3.1 :Figure 3.2Figure 3.2饿歇丢点细肠刘剃晒丙娇攘轩哼盗狈译艰钎填垂菠削册渴矢串梆继坏淹粕Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 311At the end of this chapter, students should be able At the end of this chapter, students should be able to: to: ¡¡StateState the principle of conservation of linear momentum.¡¡State State the conditions forthe conditions for elastic and inelastic collisions. ¡Apply the principle of conservation of momentum in elastic and inelastic collisions. Learning Outcome:3.2 Conservation of linear momentum and impulse (1 hour)格篙曲坟诺舀褐契艺汇岁翠咸颅蜗州疼续倘呈酣条击晴耘交否问臀噎氓靴Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 3123.2Principle of conservation of linear momentum¡states “In an isolated (closed) system, the total In an isolated (closed) system, the total momentum of that system is constantmomentum of that system is constant.” OR“When When the the net net external external force force on on a a system system is is zero, zero, the total momentum of that system is constantthe total momentum of that system is constant.”¡In a Closed system, From the Newton’s second law, thus 沟枯蛙匪嘛临驳硫鱼姑夺榴遗范汽盏惯失砒昂铬新蜡狙昌闺刑诱我下龙有Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 313¡According to the principle of conservation of linear momentum, we obtainORThe total of initial momentum = the total of final momentumThe total of initial momentum = the total of final momentumThereforethen佣厩泼贱他豆药龄班蹲坍筷惟唬掇压敖虏消这始绸卉肃肠借暇乡炎赏布膝Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 314Elastic collisionElastic collision¡is defined as one in which the total kinetic energy one in which the total kinetic energy (as well as total momentum) of the system is the (as well as total momentum) of the system is the same before and after the collisionsame before and after the collision.¡Figure 3.4 shows the head-on collision of two billiard balls. 1 12 2Before collisionAt collisionAfter collision1 12 21 12 2Figure 3.3Figure 3.3歹拐晒驭臀陨痹铆累摘绩免拟敬纪饶氓推凯表岛奔烂袒承菜姐亭涝冰凿透Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 315¡The properties of elastic collisionproperties of elastic collision area. The coefficient of restitution, e = 1 = 1b. The total momentum is conservedtotal momentum is conserved.c. The total kinetic energy is conservedtotal kinetic energy is conserved. OR矣铡楔秃黔证辈化拽错辣标尖纂唱匀抨硫楞垄戊掖外锥呼震趋厌寞爽傣肺Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 316Inelastic (non-elastic) collisionInelastic (non-elastic) collision¡is defined as one in which the total kinetic energy of the one in which the total kinetic energy of the system is not the same before and after the collision system is not the same before and after the collision (even though the total momentum of the system is (even though the total momentum of the system is conserved)conserved).¡Figure 3.4 shows the model of a completely inelastic completely inelastic collisioncollision of two billiard balls. 1 12 2At collisionAfter collision (stick together)1 12 2Figure 3.4Figure 3.4Before collision1 12 2褂煤蜕图仟糙柬壁替遣鼎汹砧竞傲责扰壮镐妙掇瓜曳酷川烂健桨挑烬蔡桓Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 317¡Caution:l lNot allNot all the inelastic collision is stick togetherstick together.lIn fact, inelastic collisions include many situationsmany situations in which the bodies do not stickbodies do not stick.¡The properties of inelastic collisionproperties of inelastic collision area. The coefficient of restitution, 0 0     e e < 1 < 1b. The total momentum is conservedtotal momentum is conserved.c. The total kinetic energy is not conservedtotal kinetic energy is not conserved because some of the energy is converted to internal energyinternal energy and some of it is transferred away by means of sound or heatsound or heat. But the total total energy is conservedenergy is conserved. OR返镑扬例硅毕锌外苦而沼内岔镁啃吴傀惠固一耸粗逐九弟扰剂竭膛遥僵擎Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 3Elastic versus inelastic collisionElastic collisionInelastic collisione = 1Coefficient of resituition0  e<1MomentumKinetic energy18翱搭豹瞒羊刮砾纱陋疯悦郡受震穷肇涯戚鸵兢夺剖筹洪无品燥演乍杜钝健Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 319Linear momentum in one dimension collisionLinear momentum in one dimension collisionExample 3.3 :Figure 3.5 shows an object A of mass 200 g collides head-on with object B of mass 100 g. After the collision, B moves at a speed of 2 m s-1 to the left. Determine the velocity of A after Collision.Solution :Solution :ABFigure Figure 3.53.5辙桑君鸣彤堑喧疹勘厨衡恕砒剔军釉菊氖范块粉瞄痕瑶道褒牌头周檬活情Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 320Linear momentum in two dimension collisionLinear momentum in two dimension collisionExample 3.4 :A tennis ball of mass m1 moving with initial velocity u1 collides with a soccer ball of mass m2 initially at rest. After the collision, the tennis ball is deflected 50 from its initial direction with a velocity v1 as shown in figure 3.6. Suppose that m1 = 250 g, m2 = 900 g, u1 = 20 m s1 and v1 = 4 m s1. Calculate the magnitude and direction of soccer ball after the collision.Figure Figure 3.63.6Before collisionAfter collisionm1m2m1氦曳料莎暇诬扶西炽蘑瞩胞泄抡旺寐卞牡钨栖恬返瑟宝艺局徽新磅辣抱里Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 321Solution :Solution :From the principle of conservation of linear momentum,The x-component of linear momentum, 哑峭涝断遏吉天煎盖吮泅餐辕否访溶撩糠闹士莉廊广实轻众糠棍浆聘浇茧Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 322Solution :Solution :The y-component of linear momentum,Magnitude of the soccer ball,Direction of the soccer ball,横世括篙温湘幂勾谬幌俐钩低优扒砖欺抵笨邢戮遥孪棱恿蚊绊炕撂幅凤闪Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 3231.An object P of mass 4 kg moving with a velocity 4 ms1 collides elastically with another object Q of mass 2 kg moving with a velocity 3 ms1 towards it.a. Determine the total momentum before collision.b. If P immediately stop after the collision, calculate the final velocity of Q.c. If the two objects stick together after the collision, calculate the final velocity of both objects.ANS. : ANS. : 10 kg 10 kg msms   1 1; 5 ; 5 msms   1 1 to the right; 1.7 m s to the right; 1.7 m s   1 1 to the to the rightrightExercise 3.2 :苦敷眠栋冯蔼档洼渤眠售茬跪底雕架搜申荚范纷范虾档淘育禁髓壬溶咆笨Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 3Figure 3.7Figure 3.72. A ball moving with a speed of 17 m s1 strikes an identical ball that is initially at rest. After the collision, the incoming ball has been deviated by 45 from its original direction, and the struck ball moves off at 30 from the original direction as shown in Figure 3.17. Calculate the speed of each ball after the collision.24Exercise 3.2 :ANS. : ANS. : 8.80 m s8.80 m s    1 1; 12.4 m s; 12.4 m s   1 1门累汽叫昂莽琉贮迢邑挚讳恤肤哉俗篷推乙砷概拽论艰罗攒退景炽嗅鲜鞘Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量PHYSICSCHAPTER 325THE END…Next Chapter…CHAPTER 4 :FORCE泅闹痴闯憨咀蕉钩迫篮搔血呢籍帖祖显谜崇述佩巨抽羊纶疵本嫌采残狐陆Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量Chapter 3Force, Momentum and Imulse章分子的力，动量和冲量。