Physics Chapter 1

(1)

Welcome to Physics!

Dr. Stephanie Atherton Room 329

Oﬃce Hours : M, T, Th 2:45 – 3:30

*shiH with blocks

(2)

Useful Online Resources

• _{Flipping Physics (}

_{www.ﬂippingphysics.com}

₎

• The Physics Classroom

(

www.physicsclassroom.com

)

• _{PhET SimulaLons (}

_{phet.colorado.edu}

₎

(3)

Chapter 1 – The Science of Physics

SecLon 1 - What is Physics?

Physics is…

- the quanLﬁcaLon of moLon and the causes for moLon, as well as the interacLons of ma^er

(4)

The ScienLﬁc Method - review ﬁgure 1.4

- most physics studies involve developing models and deﬁning a system

(5)

SecLon 2 – Measurements in Experiments

Measurements

- measurements in physics have magnitude, dimensions, and units

-magnitude is the size of the measurement

- dimensions are the type of measure

(6)

(7)

Système InternaLonal (SI)

- the standard measurement system used in science (a.k.a. metric system)

- base units for length, mass and Lme are meter (m), kilogram (kg) and, second (s), respecLvely

- refer to Figure 2.4 (page 12) for preﬁxes

(8)

ConverLng Units:

- we will use dimensional analysis, or the factor-label method

- this is one way to convert units; you do not HAVE to do it this way but it’s a versaLle method that is failproof if applied correctly

- steps:

  1) form factors of 1 using equivalences

(9)

  e.g.2) Real-life example: How many eggs are in 3 dozen? How many dozen are 72 eggs? Use dimensional analysis to illustrate the answers.

e.g.3) Convert:

a) 24 m to both Mm and to dm b) 8.2 cm to both km and to mm c) 2.7 m/s to km/h

d) 1.0 kg/L to g/mL

Homework Ch 1 part 1:

(10)

Homework Ch 1 part 1:

PracLce A page 15 #1-3, (4), 5

1. 5 x 10-5_{m  2. 1 x 10}-6_s

3. a. 1 x 10 -8_{m  b. 1 x 10}-5_{mm c. 1 x 10}-2_μm

(4) 0.15 Tm or 150 Gm; 1.5 x 108_km

5. 1.440 x 103_kg

(11)

Accuracy and Precision:

- accuracy is how close the measurement is to the accepted answer

- precision is the degree of exactness (reflected by significant figures)

e.g.4) A given piece of wood has an accepted length of 2.0 m. Of the following, which is the most accurate and which is the most precise measure? Explain.

  a) 2.023 m

(12)

Signiﬁcant Figures:

- digits in a measurements that are known, plus one esLmated digit

- the esLmated digit is the ﬁrst place aHer the smallest increment on the measuring device

(13)

CounLng Signiﬁcant Figures:

  - 4 basic rules starLng at the leH of the number  1) non-zero digits are signiﬁcant (1-9)

 2) zeros between non-zero-digits are signiﬁcant

 3) zeros aHer non-zero digits are signiﬁcant if the decimal point is included

 4) zeros before non-zero digits are not signiﬁcant

e.g.6) How many significant figures are in each of the following figures?

  a) 2200  b) 3.40

  c) 42.07  d) 100.0

(14)

Math Maintaining Signiﬁcant Figures:

  - for addiLon and subtracLon, truncate at the lowest precision

  - for mulLplicaLon and division, take the smallest number of signiﬁcant ﬁgures

e.g.7) Express each of the following to the correct number of signiﬁcant ﬁgures

  a) 72. 1 + 0.511

(15)

e.g.8) Express each of the following to the correct number of signiﬁcant ﬁgures.

  a) 314.2 + 16.36 + 762.3  

 b) 773.7 - 772.17 + 0.8122

  c) (3.2174)(4.0) + 1.0

  d) 25.73/(10.2 - 2.00)

 * note: do not round off before the final answer is aâined; will use the simple 5 and above rounding rule instead of the odd/even rule in the textbook

Homework: Ch 1 part 2

(16)

Homework: Ch 1 part 2

FormaLve Assessment page 20 #3 & 4 (explain answer!)

#3) a) 0.67 b) 14 c) 778.92 d) 797.5

#4)a) accurate & precise b) precise

(17)

SecLon 3 - The Language of Physics

Tables and Graphs:

- tables are used to organize data in columns

- graphs are used to show trends in relaLonships (linear, quadraLc, inverse, etc)

EquaLon of a Line : y = mx + b where m = Δy / Δx  

QuadraLc: y = ax2_{+ bx + c}

Inverse: xy = a

(18)

InterpolaLon and ExtrapolaLon: * not explicitly in textbook!

- interpolaLon is ﬁnding values within a given data set on a graph

(19)

 InterpolaLon-ExtrapolaLon Lab:

To be completed in laboratory notebook, following speciﬁed format outlined in class.

Procedure:

1) Measure the lengths of 5 diﬀerent pieces of wire. Measure the mass of 4 of the wires, but not the 5th_.

2 ) Make a data table to summarize your data.

3) Graph the data for the 4 wires for which both the mass and lengths are known. Include a best-ﬁt line of your data, ﬁnding its equaLon in slope-intercept form.

4) Find the mass of your 5th_{wire, using both graphical and}

algebraic inter/extrapolaLon.

5) In your conclusion, state the acLvity’s objecLve, the

(20)

Review Homework:

page 29 #6, (7), 11abdeg, 14, 19 (jusLfy), 21, 20, 22, (23 - explain), (28), (36), 37a, 39, 43

 * follow the rules for signiﬁcant ﬁgures for all problems!

AND

page 32 #3 - 8, 11

* mulLple choice pracLce - no jusLﬁcaLon/work required

(21)

6) m2_/s2 _{(7) kg/s}

11a) 200 mm b) 7.8 x 103_{s d) 7.5 x 10}4_{cm e) 0.000675 g}

g) 9.7 m/s 14) 11 people

19) a) 3 b) 4 c) 3 d) 2

20 a) 797 g b) 0.90 m/s c) 17.8 mm d) 23.7 s

21) 228.8 cm 22) 115.9 m (23) b,c

(28) not valid (36) 8 x 105_{balls 37) a) 22 cm; 38 cm}2

39) 0.09818 m 43) 1.0 x 103_kg

(22)

More PracLce!

1. Convert the following:

a)  12 m/s to km/h

b)  15 Mm to mm

2. How many signiﬁcant ﬁgures would each of

the following have?

a)  24.2 - 0.012 x 10