Lesson: Not just a regular Pendulum                                                                                 Dave Matthews

 

Background Info

 

The Pendulum unit will follow units on energy and motion.  With previous lessons just immediate to this giving students experience with working with a ‘normal pendulum, this can be an extension to help differentiate the various understanding of oscillating movement and energy transfer between potential and kinetic energies. Where each pendulum could be studied for days individually, these stations are designed just as an extension.   Student’s natural curiosity may lead to having various discussions as a group or individually about such topics like chaos or hypnosis. Assessment will be the lab questions from the stations.

 

Brief Pendulum Unit Outline

 

1)    Exert from Pit & pendulum recording. Questions about how to change the speed the death of the prisoner.

2)    Regular Pendulum: Period, Mass and Arm variables and review of energy transfer from potential to kinetic energy.

3)    Present Data Day:  Computer Expert, Presenter, Lab Tech Present information about student designed pendulum experiment from previous day.

4)    Not just a regular Pendulum: A brief study of Chaotic, Coupled, and Wilberforce Pendulums. Questions for each pendulum are included for students’ assessment.

5)    Pit & Pendulum Video

 

Stations:

 

Depending on student numbers and time, the number of stations can be increased with supplemental materials and a like the website below that models pendulums.  Also you could modify with a review station about a basic pendulum.

 

http://myphysicslab.com/index.html

 

A)   Wilberforce Pendulum

 

Building:

Legs (height) and spring length can be modified to fit your needs. Base is need to support the height of the object. Weight must be balanced in the center of the spring to ensure maximum torque. The centering is made easy by using the wire harness for the weight.

 

Directions and questions for station:

 

Gently drop the spring from the top cross bar without the weight. Then try dropping it with wheels on either side of the axle.  Repeat with different combinations of weight.

                                                                 

1)    What does the weight make the spring do?  Describe the actions of the motion very closely.

2)    How does more weight affect the spinning of the spring?

3)    What happened to the energy from the spring as it reached the end of its expansion?

4)    Is there a pattern?  Explain.

                             

 

 

 

 

B)   Coupled Pendulum

 

Building:

      As simple as it looks. Be mindful that the both arms should be equal to design a fair test. Attach both to a  wire or cable to facilitate energy transfer from each pendulum.

 

Directions and questions for station:

      Start these two pendulums from the same height.

1)    List the differences between the two pendulums.

2)    Describe what happens to each of the pendulums after swinging for a while.

3)    Using your understanding from previous pendulum experiments, explain why this is happening.

 

-OR- 

 

Pick a pendulum and just start that one in motion, leaving the other untouched on the wire.

 

Answer the same questions about this action. 

 

C)   Chaotic Pendulum

 

Building:  Probably best put by Mike, late on Thursday afternoon, “It will be a labor of love.”   I would also add… “that only Dr. Frankenstein could love.”

 

The importance of length of the arms has yet to be determined but I used the proportions of 1,2,3, and 4 for each of the arm length.  Drill bigger holes than the diameter of the screws used to enable free-swinging action.  Also use washers as needed to space the arms from one another. Place the start point just right of perpendicular to generate the most motion.

 

Directions and questions for station:

Start the single arm at the marked point on the wall. Drop. Repeat three times.

 

1)    Does the arms of the pendulums every swing in the exact same pattern from start to finish?

Change the drop position and drop 3 times.

2)    Does it follow the same pattern after dropping from a different position?

3)    Where does it end up?