# Workout: Free-body diagrams

Read the web page: Free-body diagrams.

## Launch

To give you some practice on working with forces, go to the PhET simulation Forces and Motion - Basics to perform a few tasks.

## Set up

Select one blue 50N person and a 50N red person. Move them up to the rope. Click the "Values" box but NOT the "Sum of forces". Your screen should look like the image below. For each task, decide FIRST what you think the sum of forces is and then check by turning on the "Sum of forces" checkbox. (Then turn it off for the next part.)

1. Think back to the readings for solving for Fnet. How do you find a Net Force?
2. What objects are exerting forces on the cart?
3. Draw a Free Body Diagram for the cart with vector arrows, labels and describe what it looks like.
4. What is the sum of the forces and direction for situation 2? Explain.
5. Select one blue 150N person, 100N blue person, two 50N red people. Move them up to the rope. Draw a Free Body Diagram with vector arrows, labels and describe it.
6. What is the sum of the forces and direction for situation 5? Explain.
7. Select 5 people red or blue. Move them up to the rope. Draw a Free Body Diagram with vector arrows, labels and describe it in the box below.
8. What is the sum of the forces and direction for situation 7? Explain.
9. Explain how a Free Body Diagram allows you to solve force problems.

Dave Buehrle, Fall 2016

Article 489