In this lecture, we will revisit the application of Newton's second law to a system of particles and derive some useful relationships expressing the conservation of angular momentum. Center of Mass Consider a system made up of n particles. A typical particle, i, has mass mi, and, at the instant considered, occupies the position Ti relative to a frame xyz. We can then define the center of mass, G, as the point

In this lecture, we will revisit the principle of work and energy introduced in lecture D7 for particle dynamics, and extend it to 2D rigid body dynamics. Kinetic Energy for a 2D Rigid Body We start by recalling the kinetic energy expression for a system of particles derived in lecture D17

In this lecture, we will start from the general relative motion concepts introduced in lectures D11 and D12. and then apply them to describe the motion of 2D rigid bodies. We will think of a rigid body as a system of particles in which the distance between any two particles stays constant. The term 2-dimensional implies that particles move in parallel planes. This includes, for instance, a planar body moving within its plane

An accelerometer is a device used to measure linear acceleration without an external reference. The main idea has already been illustrated in the previous lecture with the example of the boy in the elevator. Clearly, if we know the weight of the boy when the acceleration is zero, we can determine from the reading on the scale the value of the acceleration. In summary, the acceleration will produce an inertial force on a test mass, and this force can be nulled and measured with precision. Below we have sketch of a very simple one axis accelerometer

固体的分类：按原子(或分子)的聚集状态分为晶体和非晶体（可以互相转换）。晶体的特点：基本质点在空间规则排列,具有规则的外形；具有一定熔点；各向异性

Inertial reference frames In the previous lecture, we derived an expression that related the accelerations observed using two reference frames, A and B, which are in relative motion with respect to each other. aA =aB+(aA/ B)'y'' 22 x (DA/ B) 'y'2'+ TA/B+ X TA/B). (1) Here, aA is the acceleration of particle A observed by one observer, and

Non-Inertial Reference Frame Gravitational attraction The Law of Universal Attraction was already introduced in lecture D1. The law postulates that the force of attraction between any two particles, of masses M and m, respectively, has a magnitude, F, given by F= (1) where r is the distance between the two particles, and G is the universal constant of gravitation. The value of G is empirically determined to be

In the previous lecture, we related the motion experienced by two observers in relative translational motion with respect to each other. In this lecture we will extend this relation to our third type of observer.That is, observers who accelerate and rotate with respect to each other. As a matter of illustration, let us consider a very simple situation, in which a particle at rest with respect

In the previous lectures we have described particle motion as it would be seen by an observer standing still at a fixed origin. This type of motion is called absolute motion. In many situations of practical interest, we find ourselves forced to describe the motion of bodies while we are simultaneously moving with respect to a more basic reference. There are many examples were such situations occur. The absolute motion of a passenger inside an aircraft is best

So far we have used Newton's second law= ma to establish the instantaneous relation between the sum of the forces acting on a particle and the acceleration of that particle. Once the acceleration is known,the velocity (or position) is obtained by integrating the expression of the acceleration (or velocity). There are two situations in which the cumulative effects of unbalanced forces acting on a particle are of interest to us. These involve: