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 4&5 Newtonian Mechanics

485 Dynamics: Newton's Laws and applications Chapter 4&5 Newtonian mechanics 1. Newton's Law 2. Some Particular Forces 3. Applying Newton's Laws

4&5 Dynamics: Newton’s Laws and applications Chapter 4&5 Newtonian Mechanics 1. Newton’s Law 2. Some Particular Forces 3. Applying Newton’s Laws

485 Dynamics: Newton's Laws and applications New words 1 Force(力) Newton's First Law- Inertial (惯性)Law

4&5 Dynamics: Newton’s Laws and applications New Words 1 Force (力） Newton’s First Law — Inertial （惯性） Law

485 Dynamics: Newton's Laws and applications Dynamics studies the connection between force and motion

4&5 Dynamics: Newton’s Laws and applications  Dynamics studies the connection between force and motion

485 Dynamics: Newton's Laws and applications 英国物理学家,经典物理 学的奠基人.他对力学、光学 热学、天文学和数学等学科都 有重大发现,其代表作《自然 哲学的数学原理》是力学的经 典著作.牛顿是近代自然科学 牛顿 Issac newton奠基时期具有集前人之大成的 (1643-1727)贡献的伟大科学家

4&5 Dynamics: Newton’s Laws and applications 英国物理学家, 经典物理 学的奠基人 . 他对力学、光学、 热学、天文学和数学等学科都 有重大发现, 其代表作《自然 哲学的数学原理》是力学的经 典著作. 牛顿是近代自然科学 奠基时期具有集前人之大成的 贡献的伟大科学家 . 牛顿 Issac Newton （1643－1727）

485 Dynamics: Newton's Laws and applications 4-1. Force(P77-P78) 1 Force(力) An interaction(相互作用) that can cause an acceleration of a body. Unit:N(牛顿) Force is a vector, when two or more forces act on a body, the net force(合力) on a body is the vector sum of all the forces acting on it

4&5 Dynamics: Newton’s Laws and applications An interaction（相互作用） that can cause an acceleration of a body. Force is a vector, when two or more forces act on a body, the net force（合力） on a body is the vector sum of all the forces acting on it. 4-1. Force (P77-P78) 1 Force (力） Unit：N（牛顿）

485 Dynamics: Newton's Laws and applications 4-284-3. Newton's Law on Motion (P78-P79) 1. Newton’ s First law- Inertial(惯性)Law Every body continues in its state of rest or of uniform speed in a straight line as long as no net force acts on it (任何物体都保持静止或沿一条直线作匀速运动状态, 直到作用在它上面的力迫使它改变这种状态为止). ★F=0时,⑦=恒矢量

4&5 Dynamics: Newton’s Laws and applications 4-2&4-3. Newton’s Law on Motion (P78-P79) Every body continues in its state of rest or of uniform speed in a straight line as long as no net force acts on it. (任何物体都保持静止或沿一条直线作匀速运动状态， 直到作用在它上面的力迫使它改变这种状态为止). 1. Newton’s First Law — Inertial（惯性） Law v =  F = 0 时， 恒矢量 

485 Dynamics: Newton's Laws and applications Supplementary Explanation: 1惯性 质点不受力时保持静止或匀速直线运动 状态的的性质,其大小用质量量度。 The concept of Inertia(惯性): TThe mass is an intrinsic characteristic of a body, it characterizes the inertia of the body Weight is a force and mass is a property of a body itself. 2力 使质点改变运动状态的原因 The force is the only reason which ma kes the states of body change. It indicates the concept of force: An interaction -can cause an acceleration of a body

4&5 Dynamics: Newton’s Laws and applications 1 惯性 —— 质点不受力时保持静止或匀速直线运动 状态的的性质,其大小用质量量度。 2 力 —— 使质点改变运动状态的原因. The force is the only reason which makes the states of body change. It indicates the concept of force: An interaction —–can cause an acceleration of a body. Supplementary Explanation: The concept of Inertia(惯性): The mass is an intrinsic characteristic of a body, it characterizes the inertia of the body. Weight is a force and mass is a property of a body itself

485 Dynamics: Newton's Laws and applications 2 Inertial reference frames(惯性系)P79 An inertial reference frame is one in which Newton’ s laws hold O In this book we usually assume that the ground is an inertial frame.( Neglect Earth's actual astronomical(天体的) motions such as its rotation. )all frames that moves in uniform linear motion relative to inertial frame are inertial frames In fact it is a non- -inertial frame(非惯性系)

4&5 Dynamics: Newton’s Laws and applications 2 Inertial reference frames（惯性系）P79 In this book we usually assume that the ground is an inertial frame. （ Neglect Earth’s actual astronomical（天体的） motions such as its rotation.）all frames that moves in uniform linear motion relative to inertial frame are inertial frames. In fact it is a non-inertial frame（非惯性系）. An inertial reference frame is one in which Newton’s laws hold

485 Dynamics: Newton's Laws and applications 4-4.Newton's Second Law of Motion (P79-P82) 1 Newton’ s second lay The acceleration of an obiect is directl proportional to the net force acting on it and is inversely proportional to its maSs. The direction of the acceleration is in the direction of the net force acting on the object ∑F(O)=m(

4&5 Dynamics: Newton’s Laws and applications The acceleration of an object is directly proportional to the net force acting on it and is inversely proportional to its mass. The direction of the acceleration is in the direction of the net force acting on the object. 4-4.Newton’s Second Law of Motion (P79-P82) 1 Newton’s second law F(t) = ma(t)  

485 Dynamics: Newton's Laws and applications The component forms of N-II Law net.x F=ma net Unit of force Newton(N IN=1kg. m/s2

4&5 Dynamics: Newton’s Laws and applications The component forms of N-II Law: Unit of force Newton (N) 1N = 1kg · m/s2 net z z net y y net x x F ma F ma F ma = = = , ,