Objective :
Directions: First construct a rotating card device with two 3×5 file cards (or two cards 3 inches by 5 inches made from stiff paper). Following Figure 2, (i) cut an approximately two and one-half inch straight slit down the middle of one card (A), and (ii) cut a slit about one and one-half inch long in the middle of the other card (B). Fit the cards together as shown (iii), and lay them flat on the desk or table in front of you. Tape card (A) to the table with the long slit as shown (tape is dotted rectangles). Bend up the lower left and right corners of the loose card (B) to use as tabs. Pull the loose card horizontally towards you until the ends of the cuts meet to form a point of rotation. Be sure the moving card (B) can turn clockwise and counterclockwise around the point of contact. Make an X to mark the spot around which the card rotates.
3.Orient the cards in the “cross” position as shown in the drawing (iii). Place your pencil point at X. With the cards motionless, carefully draw a line on the loose card (B) along the cut-edge and directly away from you. The line you drew represents a path that is ________.
[ ]straight
[ ]curved
4.Now investigate how rotation affects the path of your pencil line. Again, begin with the cards in the “cross” position and your pencil point at X. As you slowly pull the lower left tab of the loose card (B) towards you, slowly move your pencil point away from you along the cut-edge while drawing its path on (B). The loose card is rotating counterclockwise as you do this. The line you drew is ________.
[ ]straight
[ ]curved
5.You actually moved the pencil point along a path that was both straight and curved at the same time! This is possible because motion is measured relative to a frame of reference. In this investigation, there are two different frames of reference; one fixed and the other rotating. When the pencil-point motion was observed relative to the fixed card (A) and its cut-edge, its path was ________.
[ ]straight
[ ]curved
6.When the pencil motion was measured relative to the rotating card (B), its path was ________. This apparent deflection of motion from a straight line in a rotating system is called the Coriolis Effect for Gaspard Gustave de Coriolis (1792-1843), who first explained it mathematically. Because Earth is a rotating system, objects moving freely across its surface exhibit curved paths, except at the equator. This includes air parcels moving horizontally.
[ ]straight
[ ]curved
7.Now imagine yourself far above the North Pole and looking down on the Earth below. Think of the loose card (B) as being part of Earth’s surface and that X represents the North Pole. From this perspective, Earth appears to rotate counterclockwise. You can observe the pencil point’s motion relative to the Earth’s surface (B). You see that as the pencil point moves along the cut-edge and away from the X, it draws a path on the rotating surface that ________.
[ ]is straight
[ ]curves to the right
[ ]curves to the left
8.Now imagine yourself far above the South Pole and looking down on the Earth below. Again, think of the loose card (B) as being part of the Earth’s surface and that X represents the South Pole. From this perspective, Earth appears to rotate clockwise. Rotate the loose card clockwise by pulling on the lower-right tab as you draw a line along the cut edge. You can observe that as the pencil point moves along the cut-edge and away from the X, it draws a path on the rotating card that ________.
[ ]is straight
[ ]curves to the right
[ ]curves to the left
9.The effect of Earth’s rotation on the path of objects moving across its surface is greatest at the poles, and diminishes to zero at the Equator. In summary, the Coriolis Effect causes objects freely moving horizontally over the Earth’s surface in the Northern Hemisphere to appear to curve to the ________.
[ ]right
[ ]left
10.The Coriolis Effect causes objects in the Southern Hemisphere to appear to curve to the ________ as they move freely across Earth’s surface.
[ ]right
[ ]left
***This is figure 2. Construction of a rotating card device to study the Coriolis Effect***
