# Unit 3: Body Composition

Throughout Unit 1 we used the kinematic equations to model the motion of objects and make predictions about their positions, velocities, and accelerations. In unit 2 we learned about types of models and that kinematic equations are a quantitative physical model. We also learned that body fat percentage could be estimated from skinfold measurements using an empirical model that relates those two quantities, but that the uncertainty in the result was relatively large. The Unit 3 lab will investigate a more accurate quantitative empirical model that estimates body fat percentage using the body density as input. In order to use that model, we will need to understand density and how it can be determined, which in turn requires understanding of mass, volume, density, weight, apparent weight, static equilibrium, and Archimedes’ Principle. The following chapters in this unit will introduce these concepts. The learner outcomes for this unit are listed below, and below that are some related key terms to watch out for as you complete the chapter.

### Learner Objectives

1. Compare and contrast mass, volume, density, weight and apparent weight and explain how each are measured.[2]
2. Explain how the concept of static equilibrium plays into the measurement of weight and apparent weight. [2]
3. Apply Archimedes’ Principle and density concepts to predict if objects will sink or float. [2]
4.  Experimentally determine an object’s mass, weight, volume, and density. [5]

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