1) Read: In Physics, the relationship between the experimental values is shown using a technique using graphing. The independent variable is always plotted along the x axis of the graph, and the dependent value is plotted along the y axis of the graph. do the following lab: labgraph1

2) Students are given a toy car to study uniform motion. During the experiment they record the distance d(m)
covered by the car as well as the time t(s). Their measures are recorded below:

x= time (s)	y= distance (m)
1.0	0.32
2.0	0.60
3.0	0.95
4.0	1.18
5	1.45

A) The students try to find out if there is a relationship between the distance and the time.
the time is the ____________ variable (independent ? dependent ?)
the distance is the __________ variable.

B) To find out what kind of relationship exist between the variables, you need to make a graph (graph paper).
Trace the x-y axis - Find the right scale (example:  1 unit on x-axis = 0.1 and 1 unit on y axis = 1 )
plot the points. Don't connect the dot. Label the axis. Give a title to your graph (see your index card)
Is this a linear relationship (does it look like a line ? )

C) Find the best fit line. don't connect the dot. go through (0,0)

D) Find the slope (see the lab for instructions). slope = _____ m/s
E) Can you find the relationship between y and x ? y = _____ x
since y is the distance and x the time, you can write V = _____ t.
F) the unit of the slope is m/s. The slope represent therefore the __________ of the car. (m/s or mph is the unit of _____)
The slope means that the car will cover ________ meters in one second.

3) lab fitting a line to a set (labgraph2) of data  to make prediction

4) During an experiment, a student measured the mass of 10 cm³ of alcohol.
Th student then measured the mass of 20cm³ of alcohol. In this way, the
data were collected.

x= volume (cm3)	y = mass (g)
10	8
20	16
30	24
40	32
50	40

A) plot the values given. Find the right scale and don't forget the label the axis. Give a title
to your graph. Don't connect the dot.
B) trace the best fit line (going through the origin ). slope = ______g/cm³
The slope represents the ________ of alcohol. It means that 1 unit volume of 1 cm³ has a mass of ________
or that each time you increase the volume by 1 cm³, you increase the mass by __________.
C) Find the relationship between y (the mass) and x (the volume). y = ______ x.
D) CAn you use your equation to predict the mass of x= 35cm³ of alcohol ? y = mass = __________.

5) During a class demonstration, a physics instructor placed a 1kg mass on a horizontal table was nearly frictionless.
The instructor then applied various horizontal forces F to the mass and measured the acceleration a for each force applies.
The acceleration tells you by how much the speed increases every second..
So the input is the force (N) = x  and the output is the acceleration a (m/s/s) = y.
The results of the experiment are shown in:

x=force (N)	y=acceleration (m/s/s)
5	4.9
10	9.8
15	15
20	20.1
25	25
30	29.9

A) Graph acceleration vs force : plot the points. don't connect the dots. Don't forget to label the axis and to give
a title to the graph. Find the best fit line.
B) Find the slope of the line. slope = _____ N/m/s/s
extra credits: a Newton = N  = kg/m/s/s. Find now the new unit of the slope. The slope represent the ______.

6) A) An experiment is done by students. The measure the weight (y) of different masses (x).
They report their measures in the following table:

x= mass (kg)	y=weight (N)
5	50N
15	148N
20	203N
25	249N
30	303 N

Plot the points on a graph and trace the best fit line. Find the slope of the line slope = _____N/kg
Is this number surprise you ? didn't you learn in 9th grade that, on Earth, weight = mass x 9.8 ?
the equation of the line is therefore y = _______ x. The slope represents the gravitational acceleration on EArth.

B) An astronaut conduct experiments on a distance planet to find the gravitational acceleration
of the planet. His measurements are reported in the table:

x= mass (kilograms)	y= weight (newton)
15	106
20	141
25	179
30	216
35	249

Help the astronaut to find the acceleration of this new planet. Suppose the relationship between
weight and mass is linear. y = m x. You are looking for m. (the slope of the line)

7) sometimes the linear relationship between 2 quantities is written as: y= mx + b
m is the slope of the line and b is the y-intercept. (the intersection of the line and the y axis)
let's do a short lab to better understand. labgraph3  -----

8) The weight of a person's skin is related to body weight by the equation s = 1/16 (w). where is s is skin weight and w is body weight.
A) does this equation show direct variation between body weight and skin weight ?

B) If a person calculates skin weight as s=  9 3/4lb , what is the person body weight  (solve for w)?

hint: s =9.75  use the equation to solve for w