2-5 Equilibrium of Rigid Bodies (Part 3) скачать в хорошем качестве

2-5 Equilibrium of Rigid Bodies (Part 3)

Before we end this chapter, I will introduce a method for finding the position of the centre of gravity, and explain why this method is valid. Besides, since we have mentioned "centre of gravity", I will also tell you a little bit about "centre of mass". 0:00 Opening 0:35 Finding the position of C.G. 4:40 Motion of a rigid body (Extra-curriculum) 8:08 "Point object" (Extra-curriculum) Show all topics https://bit.ly/physics_concepts_eng ------------------------------ Supplementary notes: Logic 101 (Chinese only) https://bit.ly/phy_con_supp_logic_c ------------------------------ Interactive web app: Chinese https://bit.ly/phy_con_sim_2-5-3_c English https://bit.ly/phy_con_sim_2-5-3_e Source https://bit.ly/phy_con_sim_2-5-3_s ------------------------------ Supplementary information: [Rotation and deformation of point objects] Often when we consider something as a point object, we are not interested in its rotational motion. For example, when we think about people or cars moving on a map, we only care about how their displacements change with time. However, this is not always the case. Say, when we analyze a tennis match, we usually consider the tennis ball as a point object, but the coach will certainly not ignore the spinning of the ball. The reason is, when the ball hits the racket or the ground, its spin significantly affects its motion after the impact. Another example is, when we analyze the motion of celestial bodies, we usually consider stars as point objects. However, astronomers will not ignore the spinning of a star, since it greatly affects the magnetic field around the star. On the other hand, we are often uninterested in the deformation of point objects. At the moment when a tennis ball is hit by the racket, it will be squashed, but we seldom investigate this squashing in detail. However, there are cases in which the deformation within a point object is very important. For example, we often consider an atom as a point object, but we should note that an atom actually deforms all the time, since the distribution of electrons around the nucleus is constantly changing. Although an atom is electrically neutral, as the distribution of electron changes, it can form a dipole or a quadrupole, etc, and this is the main cause that atoms attract or repulse one another. If we want to understand chemical bonds, we cannot ignore this constant change in electron distribution. ------------------------------ Acknowledgements: Royalty Free Music from https://audiohub.com #DSE #physics #mechanics #物理 #力和運動 #力學