Plane Figures: Parts of a Straight Line

Age
6-9.

Materials

 * Two strings attached to spools
 * Two scissors
 * A red felt pen.

Presentation

 * 1) Again the directress prepares the spools in her hands and invites the child to watch as the line appears.
 * 2) What is it? A line...a straight line... a straight line....
 * 3) Invite the child to find a point on this straight line and mark it in red.
 * 4) The child then takes the scissors to cut the line at the point... this is a straight line... (cut).
 * 5) Taking one spool and the point, the teacher extends the string... this is a ray... this is a ray.
 * 6) The directress identifies the other ray in the same manner.
 * 7) These two rays are equal. a ray starts from a point and goes on to infinity.
 * 8) This red point is the origin.
 * 9) Therefore a point divides a straight line into two rays.
 * 10) With the other spool the situation is repeated, with child identifying a straight line.
 * 11) This time the child is invited to make two red points on the line, and to cut the line at the two points simultaneously.
 * 12) Before the cut, the line is identified as a straight line.
 * 13) After the cut the directress takes on piece at a time.
 * 14) This is a ray. This is another ray.
 * 15) This is a line segment.
 * 16) The two red points on this line segment are called endpoints, because we can't tell which is the beginning and which is the end.
 * 17) Therefore two points divide a line into two rays and a line segment.

Variation
Classified nomenclature - after the child has put the cards with the corresponding labels, have him put them in order: origin, ray, endpoints, line segment.