Focus Question: What is the relationship
between the force of a rubber band and the
amount it stretches?
L-3
Day 1
APK (Accessing Prior Knowledge): What kind of force did
we learn about yesterday while examining the difference
between mass and weight?
What do you think the force that a rubber band exerts is
called?
Essential Question: What are the different kinds
of forces and how are they measured?
Objective: SWBAT (Students will be able to)
define elastic force by measuring the force a
rubber band exerts based on the amount it is
stretched.
What is the relationship between the force of a
rubber band and the amount it stretches?
Self: 2 ½ min http://www.online-stopwatch.com/countdown-timer/
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Group: 2 ½ min
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Class:
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Write what you know or think you know about
forces that are stretchy or springy. List some
places where you see these kinds of forces in
action.
What you know about
stretchy and springy things
Where you see stretchy and
springy things
Focus Question: What is the relationship
between the force of a rubber band and the
amount it stretches?
Prediction/Hypothesis:
Before We Begin …
1. When stretching the rubber band, be careful to not
break it or snap it back and hit somebody.
2. Make sure to keep the spring scale steady and repeat
the trial so that you are sure to get an accurate
reading.
Explore:
1.
Hold a rubber band at one end, and with a finger of your other
hand, carefully stretch the rubber band far enough to feel the force
of the pull. After doing this a few times, answer the following
questions in your notebook:
A. When you stretch the rubber band, what do you feel?
B. In what direction does the rubber band pull your finger?
2. Repeat Step 1, but pull a little harder on the rubber band. Answer
the following questions:
A. Now what do you feel?
B. What happens when you pull a little harder?
3. How could you find out how the force of the rubber band changes
as the band is stretched? Discuss this with your group.
Design a data table. You should measure and record the
force of the rubber band at 2.0 cm intervals up to 20 cm.
(0, 2.0, 4.0, 6.0, 8.0, 10.0, 12.0, 14.0, 16.0, 18.0, 20.0)
You will use this data to create a graph of stretching (cm)
vs. force (N).
STOP BEFORE GOING ON TO
QUESTION #10!
Graphing 101:
• Give each graph an appropriate title.
• Use your space wisely – data should take up much of the
space, but leave enough room for labels along the axes.
• Label horizontal and vertical axes with a description of the
data and the units of measure (N, cm, etc)
Weight vs. Mass
2
1.8
1.6
Weight (N)
1.4
1.2
1
0.8
0.6
0.4
0.2
0
1
2
3
4
5
Mass (Number of Washers)
6
7
Graphing 101 Continued:
• Plot the independent variable (the data being controlled) on the
horizontal “x-axis” and the dependent variable on the vertical
or “y-axis”.
• Set the scale for each axis with even divisions – allow for
enough space for the highest measured value to fit on the axis.
• Make sure all spaces on the x- and y-axis scales are equal.
(The scale remains constant and you don’t skip around)
• Always start at 0 on both axes. This spot on the graph is
known as the origin.
• Plot the location of each data point on the graph with a small
dot.
• Independent Variable = Stretching Distance goes on the
Horizontal Axis (x)
• Dependent Variable = Elastic Force goes on the Vertical Axis
(y)
• Draw a line that “best fits” your data points, known as the
“best fit line”. Use a ruler to do this part on your graph.
Force vs. Stretch
8
7
Force (N)
6
5
4
3
2
1
0
0
2
4
6
8
10
Stretch (cm)
12
14
16
18
20
“Reflecting On What You’ve Done” – Think
Pair Share
Homework: Read “Bungee Jumping: The
Forces Are With You” on pages 26-27 and
answer the questions that follow.
Exit Ticket:
1. What are the two kinds of forces we have
discussed so far? Name them and give an
example to go with each.
On your way out, put your exit ticket in the
folder that you feel is the most accurate.
(Green, Yellow, or Red)
Focus Question: What is the relationship
between the force of a rubber band and the
amount it stretches?
L-3
Day 2
APK (Accessing Prior Knowledge): What is an independent
variable and what is a dependent variable?
What happens to the elastic force as you stretch an elastic
band?
Word Wall:
• Dependent variable
• Independent variable
• Calibration
• Extrapolation
• Elastic Material
Reflect:
Self:
Claim
Evidence
Claim
Evidence
Claim
Evidence
Group:
Class:
Nobody is permitted to write while
we are discussing the class’s claims
and evidence. Once we have
solidified the class discussion, you
may number the correct responses
you have under “Self” and Group”
and then write in the rest you need
under “Class”.
• Rubber band stretched to 4.0 cm will have a
force of 2.0 N so if it is stretched to 8.0 cm it
will have a force of 4.0 N.
– Double the length  Double the force
Bungee Jumping: The Forces Are With You
1. What factors have to be taken into consideration when a
person wants to go bungee jumping? Does their height
or weight matter? What about the equipment?
2. In what other ways do people use elastic forces?
3. What is the history of bungee jumping?
CER