Okay, here are the steps:
* 50 miles/hour
* 1 hour = 3,600 seconds
* So 50 miles/hour = 50 miles / 3,600 seconds
* 1 mile = 5,280 feet
* So 50 miles = 50 * 5,280 = 264,000 feet
* 264,000 feet / 3,600 seconds = 73.3333... feet/second
Rounded to the correct number of significant figures, the answer is:
74 feet/second
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Physics Chapter 1 Part 1
1.
2. Physics is the study of the
motion of matter
The scientific study of the
relationships between matter,
energy, space, and time.
A basic science concerned with the properties
and behavior of matter; and the resultant
energy exchange and the laws that unite these
phenomena into a comprehensive system
9. Translations have no fixed
points at all, while
rotations have exactly one
(called a pivot point,
around which everything
rotates doesn't move at
all.
10.
11.
12.
13.
14.
15. With respect to translation
Whether you perform an experiment in New York or Los Angeles,
at the other edge of the Milky Way or in a galaxy a billion light-
years from here, you will be able to describe the results using the
same laws.
With respect to rotation
The laws look precisely the same whether we make
measurements from the bottom, top, sides, etc. - physics has no
preferred direction in space.
16. With respect to reflection
The laws of physics are the same in a right-handed system of
coordinates as in a left-handed system
With respect to time
The laws work exactly the same in experiment today as they did
on an experiment performed yesterday or last year.
17. One of Einstein’s main goals in his explanation of
general relativity was to formulate a theory in
which the laws of nature would look precisely the
same to all observers. In other words, the laws
had to be symmetrical under any change in our
point of view in space and time
18. THUS, A CONSERVED QUANTITY IS SOMETHING THAT YOU
WOULDN'T BE ABLE TO GET RID OF EVEN IF YOU WANTED TO.
19.
20.
21. The symmetry properties of a physical system are
intimately related to the conservation laws
characterizing that system
22. Noether’s theorem states that each symmetry of a
physical system implies that some physical property
of that system is conserved.
Each conserved quantity has a corresponding
symmetry
Symmetry Space translation Time translation Rotation
Conserved
quantity
Linear
momentum
Energy
Angular
momentum
23.
24. Everyone is familiar with energy but no
one knows exactly what energy actually
is
For our purposes we will define Energy as
the measure of the ability to generate
motion.
A system that has energy has the ability to
do work (motion in action).
Energy is measured in the same units
(joules) as work because energy is
transferred during the action of work.
25. The SI unit of energy is
the joule, J, (rhymes with
cool), named after the
British physicist James
Joule.
One Joule is the amount
of energy required in
order to heat 0.24 g of
water by 1 °C. (The
number 0.24 is not worth
memorizing.)
35. Einstein showed that mass itself could be
converted to and from energy, according to his
celebrated equation E = mc2, in which c is the
speed of light.
Thus we can view mass as simply another
form of energy, and it is valid to measure it in
units of joules.
The mass of a 15-gram pencil corresponds to
about 1.3 × 1015 J.
36.
37. Cosmic rays, however, are
continually striking you and your
surroundings and converting part
of their energy of motion into the
mass of newly created particles. A
single high-energy cosmic ray can
create a shower of millions of
previously nonexistent particles
when it strikes the atmosphere.
38. Mass can be defined from two
different perspectives:
1) Mass is the measure of the
amount of matter that a body
contains
2) Mass is a measure of the
inertial property of that body,
that is, of its resistance to
47. Thus, many properties of matter are expressed
quantitatively (associated with numbers)
48.
49.
50.
51.
52. . NOTE: The short forms for SI units (such as mm for
millimeter) are called symbols, not abbreviations
53.
54.
55.
56. Scientists must often deal with extremely
large or small numbers
Scientific notation is a way of expressing
very large or very small numbers which are
awkward to say and write.
57.
58.
59. Writing a number in scientific notation:
1) Put the decimal after the first digit and drop
the zeroes
2) Count the number of decimal places moved in step 1
3) Write as a product of the number (step 1) and 10
raised to the power of the count (step 2)
The Andromeda Galaxy (the closest one to our Milky Way galaxy)
contains at least 200,000,000,000 stars.
So we would write 200,000,000,000 in scientific notation as:
2.0 x 1011
This number is read as follows: "two point zero times ten to the
eleventh."
60. • Now we try a number that is very small.
• Change 0.000000902 to scientific notation
• The decimal must be moved behind the 9
• The coefficient will be 9.02
• The decimal moves seven spaces to the right,
making the exponent -7
• Answer equals 9.02 x 10-7
61. • Examples
• Write each of the following numbers in
scientific notation:
• (a) 93,000,000
• (b) .00005144
• (c) -33,452.8
62.
63. • Changing numbers from scientific notation to
standard notation.
• Change 6.03 x 107 to standard notation.
• we can simply move the decimal seven places
to the right because the exponent is 7.
• So, 6.03 x 107 = 60 300 000
64. • Now let us try one with a negative exponent.
• Ex.2 Change 5.3 x 10-4 to standard notation.
• The exponent tells us to move the decimal
four places to the left.
• so, 5.3 x 10-4 = 0.00053
65. • Express in standard form:
• 1. 1.09 x 103
• 2. 4.22715 x 108
•
• 3. 3.078 x 10-4
•
• 4. 9.004 x 10-2
•
• 5. 5.1874 x 102 (This can be tricky!)
67. Accuracy indicates how
close a measurement is to
the accepted value.
Precision indicates how
close together or how
repeatable the results
are.
68.
69. Trial #1 #2 #3 #4 #5
Student A 14.8 14.1 14.5 14.6 14.2
Student B 14.8 14.2 14.6 14.5 14.8
Student C 14.6 14.5 14.5 14.4 14.6
PRECISION AND ACCURACY -- Quiz
Consider the data obtained for the length of an object as measured by three
students. The length is known to be 14.54 cm. Which of the conclusions
summarizes the data?
a) Student A has done the most precise work and student C the most
accurate.
b) Student C has done the most precise and accurate work.
c) Student C has done the most precise work and student A the most
accurate.
d) Student C has done the most precise work and student B the most
accurate.
e) Student B has done the most precise work and student C the most
accurate.
70.
71. all measurements contain some uncertainty. Such data is reported
in significant figures to inform the reader of the uncertainty of the
measurement. We record all significant figures unto the first
uncertain number.
