Exam1 Review - Carnegie Mellon University Physics...

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Unformatted text preview: Carnegie Mellon University Physics Department 33-106 Fall08 Roy A. Briere Exam I Review Items Chapter 1: Units, Scalars, Vectors, ... Physical quantities have a type: scalar and vector are enough for us. If asked for a vector (velocity, momentum, ...): Give components, or magnitude plus direction, not just magnitude ! They also have a dimension, such as length, or length per time squared. Understand issues with and the difference between units and dimensions: Even if we know dimension, we still have to consider units: a length may be measured in meters, feet, furlongs, cm, ... It is safest to convert to standard SI (mks) units: m, kg, s. (cm, km, and are all common, but non-standard) For us, most new SI units will be combinations of these Be careful to distinguish between scalars and vectors Review the textbooks discussion on significant figures As new quantities are introduced in the rest of the course: Know which quantities are vectors, and which are scalars For example (later on): Is energy a scalar or vector? What about momentum? Always think about what signs mean ( < 0 vs. > 0), and also zero Certain manipulations are common enough to list as general mathematical tools that should eventually become as routine as basic algebra: 1) Practice manipulating dimensions: Q: What is a velocity squared divided by a distance? A: an acceleration 2) Know how to use dot (scalar) products to calculate angles cos = A B/ | A | | B | ) Evaluate with components to find cos 3) Make a unit vector from any vector A Do scalar multiplication by A by 1 / | A | In other words, A = A/ | A | 4) For a two dimensional vector A = A x i + A y j , notice the useful fact that B =- A y i + A x j is perpendicular to A (swap components and negate one) True, since A B = 0 (thus- B = + A y i- A x j is also perpendicular) 5) Scaling to any length (including unit length, but more general now) Imagine we wish that A was stretched or shrunken so that it had magnitude m , instead of its current value | A | You should be able to see that the new vector B = ( m/ | A | ) A has magnitude | A | = m and is parallel to B . Chapter 2: One-Dimensional Kinematics Try to use specific variables:...
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Exam1 Review - Carnegie Mellon University Physics...

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