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)