Playground Physics With Pendulums

In this lesson, children will investigate motion as they create a pendulum and explore gravity and force.

This lesson will help children meet the following educational standards:

Develop beginning skills in the use of science and engineering practices such as observing, asking questions, solving problems, and drawing conclusions
Explore the physical properties of objects
Use tools and technology to assist with science and engineering investigations

After this lesson, children should be more proficient at:

Developing and using models to represent their ideas, observations, and explanations through activities such as drawing, building or modeling with clay
Identifying, describing and comparing the physical properties of objects
Experimenting with the changes that matter undergoes when combined with other substances
Using nonstandard and standard scientific tools for investigation
Exploring concepts and information about the physical, earth and life sciences

Beanbag
The book, Forces: Physical Science for Kids by Andi Diehn
The book, Motion: Push and Pull, Fast and Slow by Darlene Stille
Mesh bag or clean sock
Rope or cord
Timer (optional)
Tree, playground equipment, stairwell or another supporting structure to hang the pendulum from

Read the two books—Forces: Physical Science for Kids and Motion: Push and Pull, Fast and Slow—to introduce the children to simple machines and the concepts of force, gravity, and energy.
Demonstrate how to make a “bob” by putting a beanbag or another weight inside of a mesh bag or clean sock.
Tie the bob to a cord and take the children outdoors to hang it from a tree, a piece of playground equipment or another structure so that it swings freely close to the ground.
Explain: “This is a pendulum. You can try different ways to make it work."

After the children have had some time to experiment with the pendulum, ask questions: “What happens when we release the bob with the cord stretched tight? What happens when we throw the bob? What can make the pendulum stop moving?”
Document the children's observations for later discussion.
When the pendulum is at rest, invite some children to measure how far the bob is from the ground. Then invite a child to hold the bob and step back until the cord stretches tight. Ask the child to measure again. Then ask: “Now how far is the bob above the ground?”
Invite the children to imitate the motion of the bob by moving their hands through the air.
Ask a child to release the bob while the other children count or use a timer to see how long the bob stays in motion.
Introduce the idea that gravity is an invisible natural force. Explain that gravity has the power to make hanging things come to rest instead of swinging back and forth forever. Explain that gravitational force is the reason why it takes effort to make a pendulum swing for a long time.
Ask the children if they have ever been on a swing. Explain that a swing is a type of pendulum. When the children are on a swing, they are the weight (mass) that is hanging by the swing chains. When they swing back and forth, they become pendulums!

Machine: A mechanical device that is used to make work easier
Pendulum: A mass (or weight) hanging from a string or a rod that swings freely
Simple machine: A device that has only one or two parts, but still makes work easier

Set out plastic bowling pins and encourage the children to take turns aiming the pendulum bob at the pins to knock them over.
Put a foam ball in a mesh bag and hang it so that it is about waist height for most of the children. Show them how to "play catch" with the pendulum by swinging it back and forth to each other.

Engineering Explorers