Phy71 Chapter 1.Ppt

8/13/2019 Phy71 Chapter 1.Ppt

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My House Rules

I dont mind if you sleep in my class not myloss anyway.

I dont like playing in my class I easily get

distracted. If I get distracted, I will get irritated and I may

even send you out my class.

I only want to see my laptop in class. I dontwant to see yours.

Put your phones in silent mode please.


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Chapter 1

Units, Physical

Quantities, and Vectors


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Introduction

The study of physics is important because physics is one of the

most fundamental sciences, and one of the first applications of

the pure study, mathematics, to practical situations.

WOW! Physics appears

throughout our day-to-day

experiences.

http://www.diplomaframe.com


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Solving problems in physics

Identify, set up, execute, evaluate (ISEE)


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Standards and units

Base units are set for length, time, and mass.

Unit prefixes size the unit to fit the situation.

http://blogs.middlebury.edu


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An equation must be dimensionally consistent (be sure youre

adding apples to apples).

Have no naked numbers (always use units in calculations).

Unit consistency and conversions

http://en.wikibooks.org/wiki/Engineering_Statics/Introduction


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Uncertainty and significant figures

Operations on data must

preserve the datas accuracy.

For multiplication and

division, round to the smallest

number of significant figures.

For addition and subtraction,

round to the least accurate

data.

Errors can result in your railsending in the wrong place.


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Estimates and orders of magnitude

Estimation of an answer is often done by

rounding any data used in a calculation.

Comparison of an estimate to an actual

calculation can avoid errors in final results.

http://www2.pvc.maricopa.edu


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Vectors

Vectors show magnitude and displacement, drawn as a ray.


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Vector addition

Vectors may be added graphically, head to tail.


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Vector additional II


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Components of vectors

Manipulating vectors graphically is insightful but difficult when

striving for numeric accuracy. Vector components provide a numeric

method of representation.

Any vector is built from an xcomponent and a ycomponent.

Any vector may be decomposed into its xcomponent using V*cos

and its ycomponent using V*sin (where is the angle the vector V

sweeps out from 0).


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Unit vectors

Assume vectors of

magnitude 1 with no unitsexist in each of the three

standard dimensions.

The xdirection is termed

I, the ydirection is termed

j, and the zdirection, k.

A vector is subsequently

described by a scalartimes each component.

A = Axi + Ayj + Azk


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The scalar product

Termed the dot product.


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Consider the two vectors

A. zero

B. 14

C. 48

D. 50

E. none of these

3 4

8 6

A = i + j

B = i + j

What is the dot product ?A B


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3 4

6

A = i j

B = k

What is the dot product

A. zero

B.6

C. +6

D. 42

E.42

?A B


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The vector product

Termed the cross product.


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3 4

6

A = i j

B = k

What is the cross product

A. zero

B.

C.

D.

E.

24 i +18 j

24 i 18 j

18 i + 24 j

18 i 24 j

?A B


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3 4

8 6

A = i + j

B = i + j

What is the cross product ?A B

A.

B.

C.

D.

E. none of these

6 k

6 k

50 k

50 k


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Thank you very much!

See you all next meeting.

Phy71 Chapter 1.Ppt

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