Penny in a Glass

SCIENCE CONCEPT:

Newton's First Law of Motion: objects at rest remain at rest and objects in motion remain in motion unless acted upon by an outside force.

STUDENT OBJECTIVE:

The student will discover a part of Newton's First Law of Motion: an object at rest remains at rest unless acted upon by an outside force.

OVERVIEW:

The student will use a penny, a drinking glass, and a card to discover that an object at rest remains at rest unless acted upon by an outside force.

PREPARATION TIME:

5 minutes.

LESSON TIME:

15 minutes.

TEACHER PREP:

Gather materials.

WORDS TO KNOW:

strike

flick

rest

TEACHER TEXT:

Sir Isaac Newton understood that an object will change its motion only if it is acted upon by a force. Otherwise, its motion will be unchanged. If it is moving, it will continue to move in the same direction. And if it is standing still, it will remain still. An object in motion continues in motion and an object at rest remains at rest unless acted upon by a force.

This is called inertia. Inertia is simply the scientific term for matter's property of continuing its motion (or lack of motion) until acted on by some force. This property of inertia is what is described in Newton's First Law of Motion. The famous trick in which a tablecloth is pulled off a table, leaving all the dishes, silver, and glasses in place, works exactly the same way. When the `magician' snaps the tablecloth away, all the dishes are at rest.

Because of Newton's First Law of Motion, all the items on the table tend to remain at rest. The rapidly moving tablecloth doesn't produce enough force to move the dishes very much, and so they stay on the table. (To do this trick you have to be very skilled.) This lesson is just a simple example of the tablecloth trick. The card is moved away suddenly, but the penny is left behind. At this point, there is nothing to support the penny, so it falls into the glass.

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Last modified: Tue Mar 24 15:58:25 PST 1998