What makes a swing move

A Moment of Science is a daily audio podcast, public radio program and video series providing the scientific story behind some of life's most perplexing mysteries. Learn More ». Give Now ». Noon Edition. Home Archives About Contact. Media Player Error Update your browser or Flash plugin. Sit on a swing, let someone push you, and away you go.

Potential Into Kinetic Swings work by converting potential energy into kinetic energy, then kinetic energy back into potential energy, over and over again.

Potential energy is the high part of swinging. What causes the lift? As your legs are pumping and your head is being thrown backwards, you are pulling your center of mass closer to the bar at the top and this makes you gain potential energy which turns into kinetic energy. As you swing back down, your kinetic energy is now higher at the KE max and this is what causes you to get higher and higher.

Because you are not pushing against anything, and nothing is pushing against you, you have to "create" your own energy. Units serve as guides to a particular content or subject area. Nested under units are lessons in purple and hands-on activities in blue. Note that not all lessons and activities will exist under a unit, and instead may exist as "standalone" curriculum. How do pendulums work?

Pendulums are used in many engineered objects, such as clocks, metronomes, amusement park rides and earthquake seismometers. In addition, engineers know that understanding the physics of how pendulums behave is an important step towards understanding motion, gravity, inertia and centripetal force.

Engineers apply their understanding of these motion concepts to determine the force needed to propel an object into outer space, the braking power required to stop a vehicle at high speeds, and the optimal curve of a highway ramp. Teams of engineers work on a wide range of projects and solve problems that are important to society. Each TeachEngineering lesson or activity is correlated to one or more K science, technology, engineering or math STEM educational standards.

In the ASN, standards are hierarchically structured: first by source; e. Plan and conduct an investigation to provide evidence of the effects of balanced and unbalanced forces on the motion of an object.

Grade 3. Do you agree with this alignment? Thanks for your feedback! Alignment agreement: Thanks for your feedback! View aligned curriculum. Students experientially learn about the characteristics of a simple physics phenomenon — the pendulum — by riding on playground swings. They use pendulum terms and a timer to experiment with swing variables. They extend their knowledge by following the steps of the engineering design process to desi 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. Who has been on an amusement park ride called the Sea Dragon? Or, on a similar amusement park ride that looks like a big swinging ship? To get this ride started, a strong motor pushes the ship in an upward direction.

Did you know that, after the ride is started, the motor does not need to do any more work, and the ride continues on its own? How do you think the ride stays in motion? Well, after the motor gives it an initial push, the ride uses inertia to keep moving. Inertia is the property of an object to stay moving unless it is stopped by an outside force. These amusement park rides work like pendulums.

Used with permission. Why doesn't the ride fly all the way around degrees? Well, gravity pulls the ride down when it gets high above the Earth. Even though the ride is pulled down by gravity, the inertia of the object pushes the ride right back up into the air, creating a swinging motion. Once the ride is in motion, it stays in motion unless an outside force slows it. At an amusement park, a ride like this is stopped by brakes, or else it would just keep swinging and you would be riding it long after closing time!

To explain the amusement park ride the way we just did, we used the ideas of a pendulum and Newton's first law of motion. A pendulum is a mass called a bob that hangs from the end of a rod or string, and swings back and forth. Who has heard of a pendulum before? A pendulum is made of an object with a mass, called a bob that dangles from the end of a rod or string and swings freely. The amusement park ride we just talked about is actually a huge pendulum. Can anyone think of another example of a pendulum?

Anything that swings under its own weight is a pendulum — a playground swing, a curtain cord or a carpenter's plumb. Even your own legs behave like pendulums. In fact, the most efficient way to walk is to let your legs swing at their natural rate. The time it takes for your leg to make its back and forth movement depends on the length of your legs. That's why long-legged people sometimes appear to saunter along; short-legged people, to walk briskly. Some clocks, such as a grandfather clock, have a pendulum that swings to keep track of time.

Because pendulums continue to swing without changing their speed unless acted on by an outside force, they can accurately help us measure things like time. The type of pendulum we described with the Sea Dragon ride is known as a simple pendulum , because it only moves back and forth like the swings on a playground swing set.

Another type of pendulum is a spherical pendulum , in which the bob not only moves back and forth, but in a circular motion. Can anyone think of an example of a spherical pendulum? 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.