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Chapter 1 Unit 1a

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Physics tools!

Chapter 1

Unit 1a

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- What is Physics?
- Why do scientists use the metric system, instead of the English or some other system?

- Now, you measure the length and width of your table only using your hands and or feet or some other means.
- Write down your results so we can go over them as a class.
- Compare your results with the grop next to you.
- How difficult is it to compare your results with all of these different unit systems?

Topics in Physics

The study of motion and what causes motion.

Mechanics:

The study of heat and temperature.

Thermodynamics:

The study of specific types

respective motions.

Waves and Vibrations:

The study of electricity, magnetism

and light.

Electromagnetism:

Relativity:

The study of particles moving at any speed.

The study of the behavior of

submicroscopic particles.

Quantum mechanics:

Scientific Method

1. Make observations and collect data that lead to a question.

2. Formulate and objectively test hypotheses by experiments.

Hypotheses: A reasonable explanation for observations – one

that can be tested with additional experiments.

3. Interpret results, and revise the hypothesis if necessary.

4. State a conclusions in a form that can be evaluated by others.

Controlled experiment: A experiment involving the manipulation

of a single variable or factor.

SI Standard Units

Length: meters ( m )

Time: seconds ( s )

Speed: meters per seconds ( m/s )

Acceleration: meters per second squared ( m/s2 )

Mass: Kilograms ( kg )

Prefix

Abbreviation

Value

Tera

T

1012

Giga

G

109

Mega

M

106

Kilo

k

103

Hecto

h

102

Deka

da

101

Deci

d

10-1

Centi

c

10-2

Milli

m

10-3

Micro

µ

10-6

Nano

n

10-9

Pico

p

10-12

Femto

f

10-15

Metric Multipliers

Length Conversions:

1 km = 1000 m = 100,000 cm = 1,000,000 mm

1 m = 0.001 km = 100 cm = 1000 mm

1 cm = 0.00001 km = 0.01 m = 10 mm

1 mm = 0.000001 km = 0.001 m = 0.1 cm

Time Conversions:

1 year = 365 days = 8760 hr = 5.256 x 105 min 1 day = 24 hr = 1440 min = 8.64 x 104 s

1 hr = 60 min = 3600 s

1 min = 60 s

Mass Conversions:

1 kg = 1000 gm = 1,000,000 mg

1 gm = 1000 mg = 0.001 kg

1 mg = 0.001 gm = 0.00001 k

Significant Figures

1. Zeros between other nonzero digits are significant.

50.3 m, has 3 significant digits.

2. Zeros in front of nonzero digits are not significant.

0.0008 ms, has one significant digit.

- Zero that are at the end of a number and also to the
- right of the decimal are significant.

57.00, has 4 significant digits.

- Zeros at the end of a number but not to the left of a
- decimal are significant. But we will not treat them as
- significant.

20, has one significant digit.

Convert 75 km to cm.

75 km

1 cm

= 7.5 x 106 cm

10-5 km

75 km

1000 m

100 cm

= 7.5 x 106 cm

1 km

1 m

Convert 85 cm/min to m/s

85 cm

1 m

1 min

= 1.4 x 10-2 m/s

60 s

102 cm

min

Convert 50g to kg.

50 g

1 kg

= 0.05 kg

103 g

Convert 54 mm to m.

5.4 x 10-2 m or 0.054 m

Convert 3.5 kg to g

3.5 x 103 g

Convert 105 km/h to m/s

29.2 m/s

Dimensional Analysis

?

vf and viare in m/s

t in s

a in m/s2

vf = vi + at

OK

viin m/s

t in s

a in m/s2

d in m

?

Will not work

?

vf = vi2 + 2ad

NO

?

d = vit + ½ at2

Yes

So,

What is Physics?