Pen, HOOP and the BOTTLE

Presenter: Name, Tony Wayne, Albemarle HS, twayne@albemarle.org

Va. SOL:

• PH.5: The student will investigate and understand the interrelationships among mass, distance, force, and time through mathematical and experimental processes.  Key concepts include

            …Newton's laws of motion;

National Standards:

Newtonian Mechanics

Topic/Concept

Newton’s 1^st Law of Motion: “An object at rest remains at rest…”

Materials

·      12 inch diameter wooden embroidery hoop.

·      “fat” tip marker

·      Bottle. (Pictured is a plastic juice bottle with 4 cm diameter opening at the top.

Safety Considerations

Be careful not to swing your arm and hit something or someone.

Presentation

One of the fun ways to present this is to be part magician. A magician uses misdirection.

 

Begin by balancing the hoop on top of the bottle. Then balance the marker on top of the hoop. Tell the students you are going to put the pen in the bottle without touching the pen or the bottle. Emphasize to them that to watch the pen. Swing you arm across the front of the hoop such that you grab the opposite side of the hoop. Do it fast. The pen will drop in to the bottle. Have the students to come up do the demonstration. Only demonstrate and tell them to grab the near side –not the opposite side. When they grab the near side the pen will pop up in the air. Then show them the real trick.

How the physics is demonstrated

This demonstrates inertia by the hoop’s motion. The hoop is grabbed on the near side. The hoop extends deforms by extending upwards. This pops the marker up. If the opposite side is grabbed, the hoop deforms by flattening itself. The pen then drops into the bottle. The hoop deforms because of the hoop’s inertia and flexibility. See the flash animation below for a slow motion look at what is happening.

 

Construction  and Tips Regarding the Demonstration

• Have plenty of spare hoops on hand. They will break.
• Do not substitute a plastic hoop. It does not flex enough.
• A hoop comes in two parts. The outside part has a clasp for tighten in down on the inside hoop. Throw the outside part of the hoop away and keep the inside piece for the demonstration.

Sources & References

The embroidery hoops can be purchased at Walmart in the craft section or at a craft store. Look for them near the embroidery floss. They are less than $2.00 a piece -2004 price.