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/• • •

Group: 2 ½ min • • •

Class:• • •

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:

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.

Before We Begin …

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)

1 2 3 4 5 6 70

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Weight vs. Mass

Mass (Number of Washers)

Wei

ght (

N)

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.

0 2 4 6 8 10 12 14 16 18 200

1

2

3

4

5

6

7

8

Force vs. Stretch

Stretch (cm)

For

ce (

N)

“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:

Group:

Class:

Claim Evidence

Claim Evidence

Claim Evidence

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 You1. 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