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Unformatted text preview: S olomons Study Notes College Physics 1 Mechanics & Heat Fall 2011 Solomon Weiskop PhD [ Vectors ] These Notes cover everything about Vectors you will need to know for a full twosemester course in College Physics. Study Notes are available to print out by registering at www.solomonlinetutor.com Solomon Weiskop PhD Solomons Tutoring Copyright 2011 1 1. Trigonometry In order for you to be able to work with vectors (and for other reasons, too) youll need to know some trigonometry. All the trig you will need for a full year of Physics is based on the following rightangle triangle: Under the column for Vectors Ive written the basic formulas in a form that will be most useful in our study of vectors. 2 Eqs. (i) and (ii) were obtained from the basic formulas by cross multiplication: crossmultiplication Eqs. (iii) and (iv) were obtained by taking inverses. For instance, Eq. (iv) gives you HYP in terms of ADJ and OPP. To get it from Pythagoras Theorem you need to take the square root: , which is the inverse of square: . By doing this, you undo the square on since . However, since you took the square root of one side, you must also take the square root of the other side. This yields Eq. (iv) . Likewise, Eq. (iii) gives you in terms of ADJ and OPP. To ge t it from TOA you need to take the inverse tan (or arc tan) , which is the inverse of tan. By doing this, you undo the tan on since . However since you took the of one side, you must also take the of the other side. This yields Eq. (iii) . Why the basic formulas are more convenient to work with in the form of Eqs. (i) (iv) will become clear as we now begin our discussion of vectors... 3 2. Vectors A vector is like an arrow. It is something that has magnitude and direction. Magnitude corresponds to the length of the arrow (how big it is). Direction corresponds to which way the arrow is pointing. Heres a vector: I will indicate that something is a vector by putting an arrow on top: . For the magnitude, Ill leave off the arrow: . For the direction, Ill use an angle: . [I write and not just plain in order to specify that this is the angle for the vector . Note: Here Ive chosen the angle that the vector makes with the positive xaxis. I could just as well have chosen the angle that the vector makes with the positive yaxis (or even with the negative xaxis or negative yaxis). Well discuss such possibilities in more detail soon. 4 A vector is described by two numbers (e.g. one for magnitude and one for direction) Magnitude of a vector is always a positive number An example of a vector is Velocity....
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This note was uploaded on 09/27/2011 for the course PHY 121 taught by Professor Stephens during the Fall '08 term at SUNY Stony Brook.
 Fall '08
 STEPHENS
 Physics, mechanics, Heat

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