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The scientific method comes in many
different forms but always has these
basic steps:
1. Ask a question
2. Develop a hypothesis
(An if/then statement describing what you
think will answer the question)
3. Design an experiment
4. Analyze data and draw conclusions
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Let’s do a real world example:
Timmy is a geek and is having a hard time making
friends…
He just wants to be friends with the cool kids…
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So Timmy decided to use the
scientific method:
1.
2.
3.
4.
First he asks his question:
“How can I be a cool kid?”
Then he develops a hypothesis –
an if/then statement that should answer his question or solve
his problem.
“If I take showers every day, then I can be friends with the
cool kids!”
He designs an experiment:
“I’ll take a shower every day and record how many words
the cool kids say to me each day.”
He performs his experiment for a certain amount of time
and records all his data.
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So Timmy decided to use the
scientific method:
4.
He analyzes his data and draws
conclusions:
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He made a graph to display his results:
There is a direct relationship between how many days he
showers and how much the cool kids talk to him!
Now he can draw a conclusion based on his data:
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•
Timmy concluded that he is now cool and is friends with the
other cool kids!
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In any experiment, it is important to identify the variables that are
being affected or kept the same. There are three types:
1. The Independent Variable
•
This is the what you change to see what will happen.
•
Example: For Timmy this was how many days in a row he took a
shower.
2.
The Dependent Variable
•
This is what you hope is affected by the Independent Variable.
•
Example: How many words a day the cool kids say to Timmy.
3.
Constants
•
This is everything that was not a part of the experiment but
needed to be kept constant.
•
Example: even though Timmy showered, he still never put on
deodorant or stopped playing video games for 12 hours a day.
Those variables were held constant.
Remember: This should all be a REVIEW!
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Graphs have 2 axes: the horizontal (usually called ‘x’)
and the vertical (usually called ‘y’)
Graphs will be named according to what is plotted (it
goes by the general form “Y” vs. “X”
Each axis should always be labeled and include the
proper units.
 Lines
• The general equation for a line is:
y = mx + b
(where y is the dependent variable, x is the independent variable, m is
the slope, and b is the y-intercept)
• Slope
 The equation for slope is
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What is the slope of the line in the graph?
Slope (m) = (∆y / ∆x)
m = (y2 – y1) / (x2 – x1)
First, select two points that are
far apart
Plug values into the equation:
m = (30 – 10) / (14 – 4)
m=2
So, the slope is 2, but what are
the units, and what do they mean?
In this case, the units would be (smiley faces / puppies)
or /p
And this tells us that you would get 2 smiley faces for every puppy
you see!
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What is the y-intercept of the graph and what does that
mean?
• The y-intercept is 2 and it means that even with 0
puppies you can have a happiness of 2
What is the mathematical representation (equation) for
our graph?
y = mx + b
• y = 2x + 2
or H = 2P + 2
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Identifying relationships between variables is crucial in physics.
Two variables are said to be directly proportional when they are
each affected in the same way as the other when multiplied by a
constant.
• For instance, in the equation y = kx , y and x are directly
proportional because if you were to double y, x would have to
double as well.
Two variables are said to be indirectly proportional when one
variable is affected inversely when the other is multiplied by a
constant.
• For instance, in the equation y = 1/x , y and x are indirectly
proportional because if you were to double x, y would be
halved.
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Two variables are said to be
directly related when one
variable increasing causes
the other to increase as well.
Two variables are indirectly
(inversely) related when one
variable increasing causes
the other to decrease.