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2: Applications of Integration

Last updated

Dec 20, 2021
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- 1.13: More Integration Examples
- 2.1: Work

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In the previous chapter we defined the definite integral, based on its interpretation as the area of a region in the $xy$ -plane. We also developed a bunch of theory to help us work with integrals. This abstract definition, and the associated theory, turns out to be extremely useful simply because "areas of regions in the $xy$ -plane" appear in a huge number of different settings, many of which seem superficially not to involve "areas of regions in the $xy$ -plane". Here are some examples.

The work involved in moving a particle or in pumping a fluid out of a reservoir. See section 2.1.
The average value of a function. See section 2.2.
The center of mass of an object. See section 2.3.
The time dependence of temperature. See section 2.4.
Radiocarbon dating. See section 2.4.

Let us start with the first of these examples.

2.1: Work
While computing areas and volumes are nice mathematical applications of integration we can also use integration to compute quantities of importance in physics and statistics. One such quantity is work.
2.2: Averages
Another frequent application of integration is computing averages and other statistical quantities. We will not spend too much time on this topic — that is best left to a proper course in statistics — however, we will demonstrate the application of integration to the problem of computing averages.
2.3: Center of Mass and Torque
If you support a body at its center of mass (in a uniform gravitational field) it balances perfectly. That's the definition of the center of mass of the body.
2.4: Separable Differential Equations
A differential equation is an equation for an unknown function that involves the derivative of the unknown function. Differential equations play a central role in modelling a huge number of different phenomena. Here is a table giving a bunch of named differential equations and what they are used for. It is far from complete.

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