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Engineering Mechanics
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
The free body diagram is a graphical illustration of an object or a body along with all the external forces acting on it. A sketch showing the physical situation of a system consisting of several bodies is called a space diagram. For a system consisting of several bodies to be in equilibrium, each body of the system considered separately must be in equilibrium. Figure 4.16a shows a case of mowing a lawn using a lawnmower. Figure 4.16b shows its free body diagram representing the forces acting on the lawnmower.
Mechanical Structure Including Mechanisms and Load Analysis
Published in Seong-woo Woo, Design of Mechanical Systems Based on Statistics, 2021
The free body diagram is a graphical method displaying all external forces applying on a body. There is only one position in this system defined by the variable “x” that is positive to the right. It is presumed that x = 0 when the spring is in its loosened state. As seen in Figure 5.19, there are four forces to evolve a model from the free body diagram: (1) an external force (Fe) such as air-resistance force and friction force; (2) a spring force that will be a force from the spring, k⋅x, to the left; (3) a dashpot force that will be a force from the dashpot, b⋅v, to the left; and (4) finally, there is an inertial force which is defined to be opposed to the defined direction of motion. This is represented by m⋅a to the left.
Fundamental Concepts
Published in Irving Granet, Jorge Luis Alvarado, Maurice Bluestein, Thermodynamics and Heat Power, 2020
Irving Granet, Jorge Luis Alvarado, Maurice Bluestein
In physics, when studying the motion of a rigid body (i.e., a body that is not deformed or only slightly deformed by the forces acting on it), extensive use is made of free-body diagrams. Briefly, a free-body diagram is an outline of a body (or a portion of a body) showing all the external forces acting on it. A free-body diagram is one example of the concept of a system. As a general concept applicable to all situations, we can define a system as a grouping of matter taken in any convenient or arbitrary manner. We can consider a fixed amount of mass and follow it as it changes shape, volume, or position. In such a system, the mass will have a boundary that prevents any portion of mass from entering or leaving it; and this is called a closed system. However, it still permits energy (i.e., heat and/or work) to cross the specified or denoted boundary. Figure 1.1 shows a piston-cylinder device, which is an example of a closed system. As Figure 1.1 shows, energy in the form of heat (Q) or work (W) can cross its boundary; however, the mass (m) inside the system remains constant and cannot move across the boundary. Another example of a closed system is a closed container with fluid inside or a pressure vessel used to store air at high pressure.
Visualising mechanics: washing machine dynamics
Published in International Journal of Mathematical Education in Science and Technology, 2021
Note IG is the mass moment of inertia of the washing load and Rdrum and Rwash are the drum radius and washing load radius, respectively. The washing is characterized as a sphere. The point of the free body diagram and the mass acceleration diagram, is they represent the left-hand and right-hand side of the equations of motion, as determined by Newton’s 2nd law for a translating and rotating body. Applying Newton’s 2nd law together with the assumption that the radius of the washing is small compared to the radius of the drum, so the washing is approximated to be a point mass making the mass moment of inertia zero. Applying Newton’s 2nd law in the normal and tangential direction gives the following equations of motion.