Science 10

Science 10

Physics Introduction

Real smart physics guy

Real tough physics equations

What is Physics?

► Investigates the relationship between matter and

energy

Measurements & Units

► fundamental units are the building blocks of all

other measurements

► Use SI (le Système International d'unités )

► the common SI fundamental units are metre,

kilogram, second

► derived units are units made from combinations of

Derived units

► Speed m/s, km/h ► Energy Joule

Accuracy & Precision

►Accuracy refers to how closely a measured

value agrees with the correct value.

►precision of a measurement is refers to how

close the agreement is between repeated measurements

Significant digits

►Regardless of decimal position, any of the

digits 1 to 9 is a significant digit; 0 may be significant. For example:

►123 0.123 0.00230 2.30 x 103 2.03

►Leading zeros are not significant. For

example:

►0.12 and 0.012 each have two significant

digits

►All trailing zeros are significant. For

example: 200 has three significant digits 0.123 00 and 20.000 each have five

Practice

Final Answers & Sig Digs

►When multiplying or dividing, round your

final answer to the least number of s.d. found in the question (don’t forget the units)

Final Answers & Sig Digs

►When adding or subtracting, round your

final answer to the least number of

decimal places found in the question (don’t forget the units)

►11.2 cm + 5.27 cm = 16.47 cm (16.5 cm is

Measuring and Recording

► There IS a difference between 4 cm and 4.0 cm

4 cm: actual value from 3.5 cm to 4.4 cm

Scientific Notation

►A number between 1 and 10 multiplied by

some power of 10

►4159.25 = 4.15923 x 103 ►0.02654 = 2.654 x 10-2

Common SI Prefixes

►kilo = 103 ►milli = 10-3

Scientific Notation

►3.00 x 108 m/s

Practice

►Express each of the following to 3

significant digits. ►  2.928 x 104 m/s ►  25.139 N ►  0.3800 kg

Practice

►Convert 0.003127 kg to scientific notation

with the same number of significant digits.

►Convert 1564.7 m to scientific notation with

►Convert the following measurements to the indicated units. ►  246.9 g _______kg ►  67.99 km _______ m ►  2.54 m ________ mm ►

Practice

Practice

►2.50 moles x 6.02 x 1023 atoms/mol = ?

►How to use scientific notation on your

calculator

►1.505 x 1024 atoms ►1.51 x 1024 atoms

Practice

►Light travels at 3.00 x 108 m/s, how km

does light travel in 22.0 s?

►d = vt

►d = 3.00 x 108 m/s x 22.0 s ►d = 6.60 x 109 m

Units

►Think about the number AND units of your

answer:

►is it logical for a car to take 3.55 x 1017 s to

drive to Calgary at 123 km/h?

►NO! Just how many years is this much time?

The age of the universe is 14 billion years (1.4 x 1010 _a)

Units are as

important as

the actual

► Speed of a falling object 340 m/s

(speed of sound, 1224 km/h)

► Any speed close to or faster than 3.00 x 108 m/s

(speed of light! There’s NOTHING FASTER!)

► Distance of 1.50 x 1011 m

(Distance from Earth to sun)

► A distance of 2 x 10-15 m

(size of a proton)

Graphing

► graphing data is part of data analysis

► The manipulated variable should be plotted on the

horizontal axis, and the responding variable should be plotted on the vertical axis

► The scale for each axis should be set so that it

evenly distributes the measured data using as much of the graph as possible. Scales should be easy to read and evenly divided.

Graphing

►All axes must be labelled with the variable

►The graph must have a clear title. This is

usually stated as “Responding versus Manipulated” variable, with a further descriptor to help identify the data.

►Each data point must be plotted. A small

circle may be drawn around each plotted point to indicate that it is a data point.

Lines of Best Fit

►Best-fit lines or curves pass through or as

close to as many data points as possible.

►Best-fit lines do not necessarily include the

Time (minutes)

Di

stance

(m)

Line of best fit that doesn’t go through any data points

Distance as a function of time

Di

stance

(m)

Practice Graphing

0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5

0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5

Slope

𝑠𝑙𝑜𝑝𝑒 =

=

=

►Always use points on the line that can be

read easily.

►The points selected should be far apart on

►The origin should not be assumed to be a

suitable point.

►Units and powers of 10 given on the axes

MUST be included in the calculation and final answer.

►Significant digits for the slope are

determined by the precision of the

Slope Example

Time (s)

Would these points be

good for a slope

calculation?

x

y

x_1, y₁

Slope Example

Time (s)

Would these points be

good for a slope

calculation?

x_1, y₁

x_2, y₂ 

Solution

y = 9.8629x - 0.1905 0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5 Find the slope of the practice graph 9.9 m/s Time (s) Distan ce (m)

y = 9.8629x - 0.1905 0 5 10 15 20 25 30 35 40 45 50 0 1 2 3 4 5

How far was the object at t = 2.2 s? About 22 m Time (s) Distan ce (m)

►Interpolation: obtaining a value between

know data points

►Extrapolation: the extension of a graph,

curve, or range of values by inferring

unknown values from trends in the known data.