# Workout: Newton's 2nd law

Read the web page: Newton's 2nd law.

## Launch

To give you some practice on working with forces and the second law, go to the PhET simulation Forces and Motion to perform some tasks.

## Set up

Choose the tab "Force Graphs". Use the simulation to create the following situation: Joe has just been promoted and is pushing a file cabinet down the hall to his new office. He begins by looking at the file cabinet and considering how to best go about his task (scene 1). He then begins pushing on the file cabinet, which, at first, does not move at all (scene 2). Eventually the file cabinet begins to slide across the floor, slowly moving towards Joe’s new office.

1. Draw all the forces you think are acting on the file cabinet in each scene. Discuss how your force drawings compare to the free body diagram window for each scene.

2. Why do you think the file cabinet moves in scene 3 but not in scene 1 or 2?

Now try this situation:

When Annette finishes her physics homework, she closes her book and shoves it (scene 1) to the other end of the table. The book slows down as it crosses the table (scene 2) until it eventually stops (scene 3).

3. Why do you think the book moves when Annette pushes it (scene 1)?

4. Why do you think the book continues to move when she takes her hand away from the book (scene 2)?

5. Why do you think the book no longer is moving when it comes to a stop (scene 3)?

Dave Buehrle, Fall 2016

Article 490