Inclined Plane

Physics:	Geometric Shapes, Center of Gravity
Grade Range:	Elementary School, Middle School, High School
Format:	Hands-on, Stage

This demonstration is easy to set up, and it will amaze students that the objects travel down the slope at different speeds. This demonstration can be explained in different ways for different age groups.

Materials

• Inclined Plane
• Inclined Plane Box:
  • Plastic and Metal Spheres
  • Plastic and Metal Large Hollow Cylinders
  • Plastic and Metal Medium Filled Cylinders
  • Small Aluminum Hollow Cylinder (Thin Walled)
  • Small Brass Hollow Cylinder (Thin Walled)
  • Small Brass and Aluminum Filled Cylinders
  • Small Aluminum Hollow Cylinder (Thick Walled)
  • Inclined Plane Catch Box
  • Inclined Plane Wedge

Safety Precautions

Please read the Physical Demonstration section of the Demonstration Safety page before performing this demonstration.

Demonstration

Preparation

• Set up the inclined plane: Lay the inclined plane face-up across a table. Use the wedge to set the height of the inclined plane, and set the plane to an angle between 20 and 30 degrees. Set the catch box at the end of the inclined plane, and set out all the cylinders and spheres either in front of the plane or to the side.

Presentation (Stage)

1. Ask for a student volunteer, and have them hold the two spheres and tell you which one is heavier. Ask the audience if they think that the weight of the sphere will affect how quickly it will roll down the slope, and take a quick vote. Have the student hold both spheres at the top of the inclined plane, and instruct them to release both spheres at the same time when you say "GO". Give them a "Ready, set, GO", and watch the spheres go. They will roll at the same speed!
2. Repeat step one with the large hollow cylinders. They will roll at the same speed!
3. Repeat step one with the medium filled cylinders. They will roll at the same speed!
4. Repeat step one with the small aluminum hollow cylinder (thick walled) and the small aluminum filled cylinder. They will roll at different speeds!
5. Insert the small aluminum filled cylinder into the hollow cylinder. Now give the student the small brass filled cylinder and repeat step one. They will roll at the same speed!
6. Put the sphere, a small hollow cylinder and a small filled cylinder on the inclined plane together and ask the audience to vote on which one will roll the fastest. Release all three at the same time. The sphere will finish first, followed by a filled cylinder, and last is the hollow cylinder!

Presentation (Hands-on)

1. Allow students to come up and race the different shapes. Have them race the matching metal and plastic shapes first, then have them race the different shapes to see which ones move the fastest.
2. For more curious students, have them try the following:
   • Compare the speeds of the different hollow cylinders. Why don't the hollow cylinders all move at the same speed?
   • Compare the speeds of the different filled cylinders. Why do the filled cylinders all move at the same speed?
3. Be sure to watch this demonstration, and don't allow students to throw or push the shapes down the slope.

Why This Works

COMING SOON

Additional Information

• This demonstration pairs well with the Falling Chimney, the Inertia Trick and the Gyroscopes.