David Walter - Ms. Milbradt's Science Website



PhET Simulations—Forces in 1D

On the iPad, go to PhET simulations and select the “Force and Motion: Basics” activity. Go to the “acceleration” section.

For each question play with the page for a bit before you formulate an answer.

Free Body Diagrams

1. On the box, you will see force vectors. Play with the page until you create a situation where there are 2 different colored arrows in the diagram. If you were to draw the free body diagram, there would be two more. Draw and label each arrow and what it represents.

Example: FN – normal or perpendicular force -- the force perpendicular from the surface the object sits upon

2. Explain the purpose of a free body diagram and how it is helpful to evaluate the forces acting on an object.

Review Newton’s First Law

3. Now turn off friction on the page (slider in box on right) and apply some forces to the various objects. Make observations and record them. Which object is easiest to get going? Which is the hardest? Why?

4. Keep friction off. Apply a momentary force (a force that is only applied for a moment) to the object and describe what happens. Select the boxes “Values”, “Speed”, “Masses” and “Acceleration” to aid you in a complete description of the object’s motion.

5. Describe what you have to do to stop the object.

Newton’s Second Law

6. TURN FRICTION OFF. Devise a systematic method (design a lab) to determine how force, mass and motion are related. (Hint: utilize the values read out on the page – you will have to hit the “clear” button to make it start from scratch). It will be easiest to type in a force you want. Describe your procedure below.

7. Collect data in a data table. Ensure it is in an organized format to show all data you collect.

8. Based on your data and your observations, create an equation that relates mass, force and motion. Use the simulation to test your equation.

Friction and Newton’s Second Law

9. Apply various size forces to the fridge with a small amount of friction on. Explain why the fridge does not move when the applied forces are small. Connect this to real life situations.

10. What happens to the force of friction when the fridge finally begins to move?

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