Cycles Teacher Guide

Unit

Cycles

Subject

Physical Science

Grade Level

ES5-6

Activity Name(s)

Making Sounds

Pendulums

Up and Down Motion

Being Prepared

The activities in this unit can be done with small groups of two or three students. The nature of the activities make respecting work space and being aware of noise levels. The noise level issue is particularly critical when doing "Making Sounds". One possible solution would be to have student groups collect their data one at a time or use a single computer and project the data for all students to use.

Safety

Since several of the activities require to poke holes in paper cups students need to use caution when doing this. Also care needs to be used with the swing pendulums and bouncing cups so the the marble weights aren't flying around the room.

Getting Started

Making Sounds

You will need computer with built in microphones or the ability to attach an external microphone and down load the "Sound Grapher" software. You will need to collect several plastic water or soda bottles.

Pendulums

Students will be using a position sensor to collect their data. The position sensor will need to raised on a box or stack of books to get accurate measurements. In addition you will need string, cups, and marbles or some other weights. Using a projection system to show students how to change the scale on their graphs may make for easier data interpretation.

Moving Up and Down

Students will be using a position sensor to collect their data. You will also need to collect rubber bands (size #33 works well), cups, weights (marbles will work), and an old CD or DVD. Using a projection system to show students how to change the scale on their graphs may make for easier data interpretation.

Suggested Timeline

Each activity should take one 50-60 period, with possible some additional time to debrief what they have learned about cycles.

Thinking about the Discovery Questions

Many of the things that we observe in the physical world involve cycles. The movement of sound waves, the movement of the pendulum on a grandfather clock, and the up and down motion of a spring are just some examples. A cycle is sequence of events that repeat themselves. These cycles can be simple or very complex depending on the parts and structures involved.

In the first activity "Making Sounds" use Sound Grapher software to investigate the question "What effect does adding water have on the period of the sound wave produced when someone blows across the top of the bottle?". Using the software students will measure the period, or distance between peaks, of sounds with different frequencies.

In the second activity "Pendulums" a position sensor is used to investigate the question "What effect does changing the weight and length of a pendulum have on the pendulum's period of oscillation?". The position sensor will graph the position of pendulum as they change the weight and length of the pendulum.

In the third activity "Up and Down Motion" will again use a position sensor. They will investigate the question "How does adding weight affect the up and down motion of a cup bouncing on a rubber band?". Many students will have seen or experienced the slingshot rides at carnivals and wonder what happens when a lighter or heavier person rides the ride.

Misconceptions

Misconceptions that may occur when exploring the concepts in this unit. Students may have developed a mental image of a cycle as being a closed circular series of events that always returns to the same point. As they will discover cycles are more than this and that they are looking for repeated events in a linear world of graphs.

When thinking about sound students often associate loudness and pitch as being the same thing. Loudness is the measure of decibels produce by a given event. Pitch is measured by the number of peaks in a wave in a measured time (a second).

When thinking about pendulums students often approach the problem of frequency of swings believing is the controlling factor. Through their investigations they will discover that the length of the string changes the distance the weight has to travel will change the frequency of swings.

Learning Objectives

• NGSS
  • Performance Expectations
    • 1-PS4-1. Plan and conduct investigations to provide evidence that vibrating materials can make sound and that sound can make materials vibrate.
    • 3-PS2-2. Make observations and/or measurements of an object’s motion to provide evidence that that a pattern can be used to predict future motion.
    • 4-PS4-1. Develop a model of waves to describe patterns in terms of amplitude and wavelength and that waves can cause objects to move.
  • Disciplinary Core Ideas
    • ES-PS2: Motion and Stability: Forces and Interactions
      • PS2.A: Forces and Mation
        • The patterns of an object’s motion in various situations can be observed and measured; when that past motion exhibits a regular pattern, future motion can be predicted from it. (Boundary: Technical terms, such as magnitude, velocity, momentum, and vector quantity, are not introduced at this level, but the concept that some quantities need both size and direction to be described is developed.) (3-PS2-2)
    • ES-PS4: Waves and Their Applications in Technologies for Information Transfer
      • PS4.A: Wave Properties
        • Waves, which are regular patterns of motion, can be made in water by disturbing the surface. When waves move across the surface of deep water, the water goes up and down in place; it does not move in the direction of the wave except when the water meets the beach. (Note: This grade band endpoint was moved from K–2.) (4- PS4-1)
        • Waves of the same type can differ in amplitude (height of the wave) and wavelength (spacing between wave peaks). (4-PS4-1)
  • Practices
    • Developing and using models
      • Develop a model using an analogy, example, or abstract representation to describe a scientific principle.
    • Planning and carrying out investigations
      • Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.
      • Collect data to produce data to serve as the basis for evidence to answer scientific questions or test design solutions under a range of conditions.
  • Cross Cutting Concepts
    • Patterns
      • Students recognize that macroscopic patterns are related to the nature of microscopic and atomic-level structure. They identify patterns in rates of change and other numerical relationships that provide information about natural and human designed systems. They use patterns to identify cause and effect relationships, and use graphs and charts to identify patterns in data.
    • Cause and effect
      • Students classify relationships as causal or correlational, and recognize that correlation does not necessarily imply causation. They use cause and effect relationships to predict phenomena in natural or designed systems. They also understand that phenomena may have more than one cause, and some cause and effect relationships in systems can only be described using probability.
• NSES
  • NSES Science as Inquiry – Abilities necessary to do scientific inquiry
    • Employ simple equipment and tools to gather data and extend the senses.
  • NSES Physical Science - Motions and forces
    • The motion of an object can be described by its position, direction of motion, and speed. That motion can be measured and represented on a graph.
  • NSES Science and Technology – Understandings about science and technology
    • Science and technology are reciprocal. Science helps drive technology, as it addresses questions that demand more sophisticated instruments and provides principles for better instrumentation and technique. Technology is essential to science, because it provides instruments and techniques that enable observations of objects and phenomena that are otherwise unobservable due to factors such as quantity, distance, location, size and speed. Technology also provides tools for investigations, inquiry, and analysis.
    • Tools help scientists make better observations, measurements, and equipment for investigations. They help scientists see, measure, and do things that they could not otherwise see, measure and do.
  • NSES Science as Inquiry – Understandings about scientific inquiry
    • Simple instruments such as magnifiers, thermometers, rulers, provide more information than scientists obtain using only their senses.

Discussion: Setting the Stage

• What is a cycle and what are some examples that you can think of?

  A cycle is pattern of repeated events. Some possible examples would be the water cycle or a life cycle.

Making Sounds

• What are some different sources of sounds?

  Answers may include your voice, animals, cars, radio, moving objects, etc.

Pendulums

• A swing is an example of a pendulum. Describe how a person moves after a single push.

  The person moves back and forth, never coming back to the exact spot. The swing will eventually stop if move energy is not put into the swing.

• What are the parts of the swing pendulum?

  The parts students should note are a swing point of attachment (the bar on top of the swing), the rope or chain (attaches the swing point and the bob), and the person on the seat (bob or weight).

Up and Down Motion

• When you stretch a rubber band and let go of one end describe what happens?

  When you let go of one end the band will go forward away from your hand and then come back to your hand.

Discussion: Formative Questions

Making Sounds

• What is making the sound as you blow across the bottle top?

  There is a column of air in the bottle that vibrates creating a sound. Changing the amount of water changes the length of the column changing the pitch.

• Does blowing harder or softer change the pitch if the water level in the bottle stays the same?

  The pitch should stay the same since the air column hasn't changed.

Pendulums

• Looking at the graph, explain how you can tell when the bob is moving towards the sensor and away from the sensor.

  When the bob is moving towards the sensor the graph moves closer to zero (0) on the y-axis, when it is moving away it is going towards 4 on the y-axis.

• How do measure the period of a swing?

  The period of the swing is the time between peaks.

Up and Down Motions

• If you repeat your test with the same weight but stretching the rubber band more or less would the graph change?

  The the peaks and valleys will be different, but the period should be similar.

Discussion: Wrapping Up

Making Sounds

• Suppose you wanted to play a song with 8 notes, how many different water levels would you need to make the 8 notes?

  You would need 8 identical bottles with 8 different water levels.

• How is the pitch related to the size of the air column in the bottle?

  The larger the air column the lower the pitch (greater distance between peaks). The smaller the air column the higher the pitch (shorter distance between peaks).

Pendulums

• Based on your data, could you build a pendulum timer for a given time period? Explain.

  You could make a fairly accurate timer by changing the length of the string until you get the desired number of cycles in a given time (a 1 meter string will produce a 1 second timer).

• How do you think you would make a grandfather clock keep accurate time?

  By adjusting the length of the pendulum. Grandfather clocks would require you to wind them periodically to maintain the energy to keep the pendulum moving.

Up and Down Motion

• How is the motion graphed in the "Pendulum" activity similar to the motion graphed in "Up and Down Motion"?

  Both show a periodic motion of the objects. In "Pendulums" it is back and forth and in "Up and Down Motion" is up and down movement.

Additional Background

Since this unit focuses on physical cycles and how they are measured it is important to keep in mind that we are looking for a repeated pattern as recorded on a graphs. For this reason it is important that students understand that similar looking graphs can represent vary different sets of data. Understanding the x- and y-axis on a graph is important to understanding what the graph is showing. In the graphs in the activities "Pendulums" and "Up and Down Motion" the x-axis (horizontal) represents time and the y-axis (vertical) represents the distance from the sensor. In the two activities students can observe the motion that is being recorded. The results reflect the forces acting on the system created by the spring (rubber band) and the pendulum. Both are examples of periodic motion which simple describes the back and forth motion observed.

Analysis

Making Sounds

1. Referring to the sound graphs you made, how would you describe their general shape?

   The general shape is smooth wave.

2. What is the connection between the period of a sound wave and the pitch of that sound?

   The shorter the period the higher the pitch. The longer the period and lower the pitch.

3. Is there a connection between the period of a sound wave and the amount of water in the bottle? If so, describe that connection.

   The more water the shorter the period resulting in a higher pitch. Less water will create a longer period and lower pitch.

Pendulums

1. How would you describe periodic motion to someone who did not know what it was?

   It is the regular predictable movement of an object (back/forth, up/down).

2. How did the period of your pendulum change when you changed the weight in the cup?

   There was no measurable change in the period.

3. How did the period of your pendulum change when you changed the length of the string?

   The longer the string the longer the period. The shorter the string the shorter the period.

Up and Down Motion

1. How would you describe the motion of a weighted cup on the end of a rubber band?

   The cup moves up and down with some side to side movement.

2. Describe the differences between the three graphs you made. Each graph was made using a different amount of weight in the bouncing cup.

   The height of the peaks and valleys differ and the period changed.

3. What was the period of the fastest up and down motion you graphed? What was the period of the slowest? (You might want to expand the Time axis by grabbing it with the cursor and dragging to the right. This spreads the axis out so you can view smaller and smaller units of time.)

   Answers will vary but should reflect the data collected.

4. Looking at each of your graphs, what did you notice about the amplitude of the cup's motion as time went on?

   It eventually approaches zero (0).

Further Investigation

Making Sounds

Students design simple musical instruments and investigate the varying frequencies and wave lengths produced by the instruments with the CC Sound Grapher.

Pendulums

Having explored a single pendulum system introduce The Kinetic and Potential Energy of a Pendulum model (http://itsi.portal.concord.org/diy/models/99 - from the ITSI model library) and allow students to explore and try to explain the motion that is produced.

Up and Down Motion

Consider extending the lesson by having students use different size rubber bands and the same weight and compare the periodic movement graphed.