The following Activities are for the Box-on-Table applet. Make sure you know how the applet functions by consulting Help, Assumptions, and ShowMe under Applet Help on the applet's Help menu.

Activity 1. The purpose of Activity 1 is to learn to identify the Newton's-third law reaction force corresponding to a given force.

Exercise 1. Review Newton's third law.

Keep in mind that a force and the corresponding reaction force always act on different objects, never on the same object. Thus, a force and the corresponding reaction force always occur in different free-body diagrams.

Also, an action force and its reaction partner always arise from one and the same interaction between two objects. Thus, if the interaction involved is gravitational in nature, both the action and the reaction force are gravitational forces. Or, if the action force is a normal contact force, then so is its reaction partner.

Exercise 2. RESET the applet. Set the applet to the Reaction Force mode.

Use the Force drop-down menus to select the gravitational force exerted by the earth on the box.

In your Notebook, make a drawing of the box-table-earth system. Also, start making free-body diagrams for the box, the table, and the earth by drawing a dot for each of these elements of the system, labeling the dots "Box", "Table", and "Earth" as in the applet.

Both in your drawing of the box-table-earth system and in the appropriate free-body diagrams, draw the arrows representing the gravitational force exerted by the earth on the box and the corresponding Newton's-third-law reaction force. The tail end of a force vector should be placed at the point where the force is acting, which effectively is the center of gravity of an object in the case of a gravitational force acting on the object.

Use the Force drop-down menus to select the gravitational force exerted by the earth on the box.

Write down the verbal description of the reaction force.

SUBMIT your selection, and compare the applet's response with what you have drawn and written.

Exercise 3. Continuing from Exercise 2, one of the two force vectors included in the applet's free-body diagram for the box, the gravitational force vector, is shown selected in green while the other vector is unselected and shown in grey. Select the unselected grey vector with the Force drop-down menus, and add this other force vector and the corresponding reaction force to your free-body diagrams and your drawing of the box-table-earth system.

SUBMIT your entry, and compare the applet's response. Does the applet select the previously unselected vector in the free-body diagram of the box? If so, you have correctly identified this force by its verbal description. If not, change your selection and SUBMIT again.

Does the applet indicate the reaction force that you have in your drawings?

Exercise 4. Repeat Exercises 2 and 3 for the forces in the free-body diagrams for the table and the earth.

Activity 2. The purpose of this Activity is to provide further practice with Newton's-third-law reaction forces. This time, the applet will randomly select a force and you are expected to select the corresponding reaction force.

Exercise 1. RESET the applet. Select the Reaction Force Review mode.

The applet chooses a force by selecting both the force vector in one of the three free-body diagrams and the verbal description of the force via the Force drop-down menus.

Respond by selecting the corresponding Newton's-third-law reaction force either in one of the free-body diagrams or from the Reaction Force drop-down menus. Also add the force chosen by the applet and the reaction force chosen by you to your drawings.

SUBMIT your response. If the applet responds with "Correct" in the Answer Quality text field, click NEXT and continue with the next force. Otherwise, change your response and SUBMIT again.

Exercise 2. Continue in this manner until the applet has gone through all eight forces indicated in the three free-body diagrams.