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9.6:

Composite Bodies

JoVE Core
Mechanical Engineering
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JoVE Core Mechanical Engineering
Composite Bodies

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A composite body is a combination of bodies with simpler shapes connected to form a whole entity. Knowing the center of gravity of each part and its weight, the center of gravity of the composite body can be determined. If the density of the composite body is constant, its center of gravity coincides with the centroid of the body. A hammer is an example of a composite body with different densities. It consists of two main parts, each with its own weight and center of gravity. To find the center of gravity of the hammer, the weight and center of gravity of each part are taken into account. Evaluating the center of gravity of a hammer helps predict its performance. If it is closer to the head, the hammer is better for driving nails, while if it is closer to the handle, it is easier to hold and control the hammer for precision work.

9.6:

Composite Bodies

A composite body is a body made up of multiple parts, connected to form a larger, unified object. Each part has its own weight and center of gravity, which must be considered to determine the center of gravity of the composite body. In cases where the density or specific weight is constant, the center of gravity coincides with the centroid.

Composite bodies have widespread applications in mechanical engineering, from automobiles to aircraft to rockets. For example, an automobile wheel comprises a rim and spokes connected to form a single unit. Calculating its center of gravity requires knowledge about the individual parts' weights and center of gravity locations. Similarly, an aircraft wing may consist of multiple components, such as ribbing and spars, which can also be considered composite bodies. Once these parts have been accounted for, a calculation can be done to determine the aerodynamic center, which affects how the wing performs in flight. Another application is in rockets, where composite materials are used for fuel tanks due to their lighter weight compared to other options. By determining the center of gravity accurately, engineers can reduce vibration and enhance stability during launch.

Suggested Reading

  1. Hibbeler, R.C. (2016). Engineering Mechanics: Statics. Fourteenth Edition, New Jersey: Pearson. Section 9.2, Pp. 488-489.