Units, Forces, Motion and the Inclined Plane
First things First: Units

Ratios, Proportions, and Rates

Chain Calculations

Dimensional Analysis

Motion and Forces

Terms to Research
Your first physics module may seem overwhelming. All at once you are introduced to units, dimensional analysis,
vectors, and force and motion. What is it all about? Fundamentally, physics is about measurement. Physics gives
you tools that allow you to answer specific questions such as “how fast?”, “how far?” or “how much?” To give an
example, consider the design of a modern jet airliner. Suppose you were put in charge of selecting engines to power
the airliner. You will have many questions to answer such as “How big should these engines be?” Too big and they
may be too heavy for the wings or use too much fuel—so the plane would not be able to fly very far. Too small and
the plane will never be able to take off in the first place. As you can see, answers to these design questions requires
the ability to measure, to quantify, and to calculate very precisely quantities such as weight, force, gravity, velocity
(speed) and motion.
This week's module will lead us from a basic understanding of units and measurement to the quantification of
motion and forces. Our study will culminate in a lab activity in which we examine the behavior of a mass on an
inclined plane. This is a classic problem in physics, and it is important that we focus our study so that we will have a
good feel for how to solve this type of problem. There is significant supporting material in chapters 13 of the text,
so be sure to become familiar with it and do the ungraded homework exercises. Practice makes perfect, so doing the
homework assignments is essential to being able to master the lab as well as the quiz problems.
First things First: Units
A fundamental rule in physics is that “if you try to add Apples and Oranges, you will end up with ‘Fruit Salad’”.
Think of this line whenever you are given a problem in one set of UNITS, and are required to give an answer in
another set of UNITS. Chapter 1 of the text introduces you to the different local and world standards associated with
measurement units.
One thing scientists learn early on is that it is very difficult to get accurate measurements. It is no small wonder that
Archimedes, Galileo, and Newton discovered so much about our world with out the aid of tools to accurately
measure
time, distance,
and
mass
(used in mechanics). By today's standards their results are extraordinary by any
metric. The most commonly used system of measuring units is called the Metric System; on page 9 of the textbook
Table 1.1 lists the
SI Base Units
used in mechanics plus four additional units. All other units of measurement are
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 Spring '11
 DanielHale
 Physics, Force, First things first

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