Why are pendulums useful

At this point, simply gather and keep a good record of students' current ideas; students will have a chance to refine these after the website exploration that follows.

Many students believe that changing any of the variables string length, mass, or where we release the pendulum will change the frequency of the pendulum.

Give them a chance to debate and discuss their answers before continuing. After students have explored these sites, review with them their list of answers to the initial questions about pendulums, revising it with the current information based on the students' exploration of the websites.

As you review their answers to the question, "What variables affect the rate of a pendulum's swing? Begin this part of the lesson by telling students that they will explore websites to learn more about how pendulums help us learn about gravitational forces.

In the second part of the lesson, students will work in groups to construct their own pendulums and test what they have observed on the websites. Have students run the demonstration called the Pendulum Lab. With this lab, students can play with one or two pendulums and discover how the period of a simple pendulum depends on the length of the string, the mass of the pendulum bob, and the amplitude of the swing.

Make sure they understand how to run the experiment by telling them the following:. With this demonstration, you can observe how one or two pendulums suspended on rigid strings behave. You can click on the bob the object at the end of the string and drag the pendulum to its starting position. Also, you can adjust the length and mass of the pendulum by adjusting the the controls in the green box on the right side of the page.

The pendulum can be brought to its new starting position by clicking on the "Reset" button. You also can measure the period by choosing the "photogate timer" option in the green box.

Explain the features of this demonstration to your students:. In this demonstration, you can vary the length of the pendulum and the acceleration of gravity by entering numerical values or by moving the slide bar. Also, you can click on the bob and drag the pendulum to its starting position. This demonstration allows you to measure the period of oscillation of a pendulum. Students can also measure the frequency of a pendulum, or the number of back-and-forth swings it makes in a certain length of time.

By counting the number of back-and-forth swings that occur in 30 seconds, students can measure the frequency directly. Ask students:. At this point, students should understand that gravitational forces cause the pendulum to move. They should also understand that changing the length of the bob or changing the starting point will affect the distance the pendulum falls; and therefore, affect its period and frequency.

Divide students in cooperative groups of two or three to work together to complete this activity. As outlined, students will first make predictions and then construct and test controlled-falling systems, or pendulums, using the materials listed and following the directions on the worksheet.

This controlled-falling system is a weight bob suspended by a string from a fixed point so that it can swing freely under the influence of gravity. If the bob is pushed or pulled sideways, it can't move just horizontally, but has to move on the circle whose radius is the length of the supporting string.

It has to move upward from where it started as well as sideways. If the bob is now let go, it falls because gravity is pulling it back down. It can't fall straight down, but has to follow the circular path defined by its support.

This is "controlled falling": the path is always the same, it can be reproduced time after time, and variations in the set-up can be used to test their effect on the falling behavior. Note: Make sure that the groups understand that by changing the value of only one variable at a time mass, starting angle, or length , they can determine the effect that it has on the rate of the pendulum's swing. Also, students should be sure the measurements with all the variables are reproducible, so they are confident about and convinced by their answer.

After students have completed the experiments, discuss their original predictions on the activity sheet and compare them with their conclusions based on the data and the results of the tests. Older students should probably learn how the downward force of gravity on the bob is split into a component tangential to the circle on which it moves and a component perpendicular to the tangent coincident with the line made by the supporting string and directed away from the support.

The tangential force moves the bob along the arc and the perpendicular force is exactly balanced by the taut string. Now, based on these observations, determine what conclusions students can make about the nature of gravity. Students should conclude that gravitational force acting upon an object changes its speed or direction of motion, or both. If the force acts toward a single center, the object's path may curve into an orbit around the center. Assess the students' understanding by having them explore the Pendulums on the Moon lesson, found on the DiscoverySchool.

Students should click the link for "online Moon Pendulum," found under the "Procedure" section of the lesson. A tether ball moves as a spherical pendulum. Another example is an amusement park ride that spins you in a big circle.

This amusement park ride works like a spherical pendulum. All rights reserved. Why does a pendulum stay in motion? More than years ago, an Englishman named Isaac Newton described the natural behavior of motion and gravity in our world, in what he called the "three universal laws of motion. So, something that is moving keeps moving until something else stops it.

Does this remind you of the Sea Dragon ride? Or, have you ever been able to stop ice skating or roller skating without the help of an outside force perhaps dragging your foot or crashing into someone? Or, how do you stop when you are swinging on a playground swing?

Sometimes moving objects seem to stop without the help of an outside force. For example, if you slowly roll a ball across the floor, it eventually stops on its own. Does that mean Newton's first law of motion does not always hold true? The floor has roughness or friction — a resistance to motion — that slows the ball.

In this case, friction is the outside force that stops the ball from rolling. Pendulums work so well because they move through air, which has very little friction. Engineers often incorporate the ideas of the pendulum and Newton's first law of motion when they design things that we use everyday or that help people in some way. In fact, engineers always must consider the "invisible" natural forces acting on objects in motion, such as inertia, to keep us safe.

What are some ways that an engineer might be able to use a pendulum? The continuous swinging of a pendulum keeps time for some clocks. Engineers use pendulums in designing lots of things, from clocks to amusement park rides. Some engineers who study the Earth and earthquakes, design equipment and sensors such as seismometers, which use the idea of a pendulum to measure earthquakes.

Understanding pendulum mathematics helps engineers determine how much swaying back and forth a building can safely withstand during a windstorm or earthquake. If a building might build up too much inertia moving it back and forth, then engineers must figure out ways to safely counteract the movement to protect the people and property.

Real-world applications like these make the pendulum and inertia important concepts for engineers — and you — to understand.

To help convey the lesson's content, refer to the associated activity Swinging with Style where students experientially learn about the characteristics of pendulums by riding on playground swings. Newton's three laws of motion make up the foundation for the known physics of motion.

The first law states that an object in motion stays in motion and an object at rest stays at rest, unless acted upon by an outside force. This is the concept of inertia. For example, a book falls until it hits a table, and then the book stops falling because an outside force stopped it from its original path of motion. One of the greatest forces acting on our planet is the force of gravity. This is the force that holds objects down to the Earth, keeping them from flying off into space.

In the case of a pendulum, gravity is the force pulling the mass down, while inertia is the property keeping the mass in motion and pulling it back up. When sitting on a swing, the swing does not move until you are pushed or you pump your legs, creating the force that sets you in motion. But, you continue swinging, without extra pumping, until the friction of the air and the swing chain resist the motion.

Gravity pulls you down, and inertia keeps you moving until friction intervenes b. The motion of a pendulum was first mathematically described by the Italian Galileo Galilei in the late s. Galileo also investigated how things fall, how planets move, and many other natural scientific phenomena. Many of his discoveries grew out of his observations of how a pendulum swings. As explained by Galileo, we know that the period of a pendulum can be described mathematically by the following equation:.

Note that this equation does not include terms for the mass of the pendulum or the angle it swings through. The only factor that significantly affects the swing of a pendulum on Earth is the length of its string. For more about the mathematics behind the swing of a pendulum, see the sixth-grade TeachEngineering Swinging on a String lesson.

Now that we've learned all about pendulums and Newton's first law of motion, can you explain how the Sea Dragon or big boat swing amusement park ride works? Remember, a pendulum is made of an object with a bob that dangles from the end of a rod or string and swings freely. Newton's first law tells us that an object at rest stays at rest without outside interference , so a motor must first push the amusement park ride up into the air.

Then gravity pulls the ride back down. The ride has inertia, which keeps it in motion. The ride moves up and down with the help of inertia and gravity. The only thing that can stop the ride is friction, which is supplied from the brakes. Would you want to design an amusement park ride? What ideas do you have? How else do engineers use the ideas they get from pendulums and Newton's first law of motion? Engineers incorporate pendulums in many projects — such as designing clocks, designing amusement park rides, studying the Earth and earthquakes with seismometers, and determining how much swaying movement a structure or tower can safely withstand during storms.

Now that you know how a pendulum works, if you can convince the amusement park ride operator not to use the brakes, you could stay on the amusement park ride for even longer! Newton's first law of motion: An object in motion stays in motion and an object at rest stays at rest, unless acted upon by an outside force. Often used to regulate devices, such as clocks. Point out the characteristics of a pendulum, and have them think about why pendulums behave the way that they do.

Engage the class in open discussion, respectfully listening to all ideas. Ask students to watch carefully. Then release the swing pendulum. Ask the students:. After-Playground Math Practice: Have the students fill out the attached Graphing Worksheet and discuss how string length and start angle affect the speed at which the pendulum swings!

Amusement Park Engineering : What are some pendulums that engineers help to design? Amusement park rides, clocks, earthquake seismometers, etc. Give the right answer. Human Matching: On ten pieces of paper, write either the term or the definition of the five vocabulary words. Ask for ten volunteers from the class to come up to the front of the room, and give each person one of the pieces of paper.

One at a time, have each volunteer read what is written on their paper. Have the remainder of the class match term to definition by voting. Have student "terms" stand by their "definitions. As a library research project, have the students research Galileo Galilei. What other scientific findings did he make during his lifetime? Have the students' research the ways that engineers use pendulums today. Some suggestions: seismographs, inertial dampeners, in sky-scrapers.

Gamow, George. The Great Physicists from Galileo to Einstein. Wolfson, Richard and Jay M. Physics: For Scientists and Engineers. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.

Why Teach Engineering in K? Find more at TeachEngineering. Quick Look. Print this lesson Toggle Dropdown Print lesson and its associated curriculum. Suggest an edit. Discuss this lesson. Curriculum in this Unit Units serve as guides to a particular content or subject area.

Rocket Couch Potato or Inertia Victim? Ring around the Rosie Super Spinners! TE Newsletter. Subscribe to TE Newsletter. Summary Students explore how pendulums work and why they are useful in everyday applications.

In a hands-on activity, they experiment with string length, pendulum weight and angle of release. In an associated literacy activity, students explore the mechanical concept of rhythm, based on the principle of oscillation, in a broader biological and cultural context — in dance and sports, poetry and other literary forms, and communication in general. Engineering Connection Engineers know that understanding the physics of how pendulums behave is an important step towards understanding all kinds of motion.

Knowledge gained from other fields of study has a direct effect on the development of technological products and systems. Grades 6 - 8 More Details View aligned curriculum Do you agree with this alignment? Colorado - Math Solve real-world and mathematical problems involving the four operations with rational numbers.

Grade 7 More Details View aligned curriculum Do you agree with this alignment? Solve linear equations and inequalities in one variable, including equations with coefficients represented by letters. Grades 9 - 12 More Details View aligned curriculum Do you agree with this alignment?

Predict and evaluate the movement of an object by examining the forces applied to it Grade 8 More Details View aligned curriculum Do you agree with this alignment? Use mathematical expressions to describe the movement of an object Grade 8 More Details View aligned curriculum Do you agree with this alignment? Lower Elementary Lesson.

The Science of Swinging Students learn what a pendulum is and how it works in the context of amusement park rides. The Science of Swinging. High School Lesson. Into the Swing of Things After watching a film clip of the "Galloping Gertie" bridge collapse and a teacher demo with a simple pendulum, student groups discuss and then research the idea of motion that repeats itself—specifically the concepts of periodic and harmonic motion.

Into the Swing of Things. Middle School Activity. Swing in Time Students examine the motion of pendulums and come to understand that the longer the pendulum string, the fewer the number of swings in a given time interval.

Swing in Time.