Tham khảo tài liệu 'sat ii physics (gary graff) episode 1 part 4', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 2 MECHANICS STATICS Objects that are not free to move are said to be in equilibrium. For an object to be in equilibrium the following two conditions must be met 1. All the applied forces must equal zero. 2. All the applied torques must equal zero. Let s stop a moment to give a quick definition for force. A force is a push or a pull. That s all there is to it a push or a pull. All forces occur in pairs and the force pairs act on different bodies. When a force is directed toward a point of contact the force is called a compression. When a force is directed away from a point of contact the force is called a tension. Using what we know about vectors we can see that every set of forces can be resolved into just three lines of action along the x axis the y axis and the z axis. We can restate the above called the First Condition of Equilibrium in the following manner YF 0 This can be broken down to address the three axes individually. YFx 0 YFy 0 YFz 0 The symbol Z is read as the sum of. We ll use it to state the conditions of equilibrium mathematically. The x axis is horizontal side to side the y axis is vertical up and down and the z axis is altitude in and out . Peterson s . com CHAPTER 2 Book Example One illustration of the first condition of equilibrium is a book resting on a flat surface as shown above. The book rests on the surface with a force equal to its weight say 10 N. The surface doesn t collapse or push the book away from itself which means that the surface is pushing back on the book with a force equal to the force the book exerts on it. The book is in equilibrium. This statement can be shown as an equation. YF 0 EFx 0 EF 0 YFz 0 Solution Looking at the individual axes 0 there are no x forces 0 there are no z forces 0 F. - F. 0 book surface F surface YFx YFz EFy F book Peterson s SATIISuccess .
