Stress is generally defined as force per unit area. Stress is a quantity that describes the magnitude of forces that cause deformation. In the language of physics, two terms describe the forces on objects undergoing deformation: stress and strain. Deformation is experienced by objects or physical media under the action of external forces-for example, this may be squashing, squeezing, ripping, twisting, shearing, or pulling the objects apart. Even very small forces are known to cause some deformation. A change in shape due to the application of a force is known as a deformation. Similarly, someone who designs prosthetic limbs may be able to approximate the mechanics of human limbs by modeling them as rigid bodies however, the actual combination of bones and tissues is an elastic medium.įor the remainder of this chapter, we move from consideration of forces that affect the motion of an object to those that affect an object’s shape. However, under other circumstances, both a ping-pong ball and a tennis ball may bounce well as rigid bodies. For example, a ping-pong ball made of plastic is brittle, and a tennis ball made of rubber is elastic when acted upon by squashing forces. The extent to which an object can be perceived as rigid depends on the physical properties of the material from which it is made. It is very useful when analyzing mechanical systems-and many physical objects are indeed rigid to a great extent. Describe the types of elastic deformation of objects and materialsĪ model of a rigid body is an idealized example of an object that does not deform under the actions of external forces.Explain the concepts of stress and strain in describing elastic deformations of materials.By the end of this section, you will be able to:
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