FinalStudyGuide

FinalStudyGuide - Physics 121 Study Guide for Final Exam...

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Physics 121 – Study Guide for Final Exam The purpose of this document is to give you a better idea of what you do and do not need to know for the final exam. I’ll try to make it all clear, but if you have any questions, please ask me during office hours or else send me an email. Part 1: Fundamentals of motion and forces We started out talking about some very basic things: modeling an object as a point particle with a definite position, setting up a coordinate system to describe that position quantitatively and representing how the position changes over time with either a ―motion diagram‖ (a bunch of dots representing the position at a sequence of points in time) or a graph of position versus time, i.e. x(t). The graphical approach helped us to interpret velocity as the slope of the x(t) graph, and we went on to talk about acceleration and its similar relationship to velocity. You should know the distinction between average velocity (or average acceleration), averaged over a time interval, and instantaneous velocity (or instantaneous acceleration) at some point in time. In general these are vectors, but in the first part of the course we focused on one-dimensional situations so they could be represented by signed scalar values. You should be very comfortable by now with the relationships among position, velocity and acceleration, and how to take a graph of one and sketch from it a graph of the other(s) based on the appropriate slope or area-under-the-graph relationship. You should also be able to tell from a graph whether each of these quantities is positive, negative or zero at a given point in time. Moving on from graphical relationships, you should be able to solve problems using the special case of constant acceleration and the even more special case of constant velocity (i.e. zero acceleration) using the definitions of these quantities plus a couple handy kinematics formulas. Newton’s laws of motion provide the powerful foundation for understanding why things move— or do not move. You should know the three laws and how each one applies to a given physical situation. In particular, a given object will accelerate if and only if there is a nonzero net force, where the net force is the sum (as signed scalars in one dimension, or as vectors in general) of all of the forces acting on that object . Note that an object moving with constant velocity (or else at rest) must have zero net force acting on it, i.e. it is at equilibrium. We talked about several types of forces which you should be comfortable working with: Force of gravity (i.e., weight) – always present and with magnitude mg (downward!) near the surface of the Earth; has a different magnitude in orbit or near other planets, etc. Spring force – know how the force it applies (at both ends!) depends on the extension or compression of the spring and on a spring constant k (Hooke’s law).

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FinalStudyGuide - Physics 121 Study Guide for Final Exam...

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