Lab 7: Static Equilibrium

General Physics 1 Lab - PHY 2048L Name __________________________ Lab 7: Static Equilibrium – Physics Motion PhET Lab Date ___________________________ Static Equilibrium Author: Harsh Jain / PhET Sources: Part 1: Balancing Act http://phet.colorado.edu/en/simulation/balancing-act Part 2: Torque http://phet.colorado.edu/en/simulation/torque Part1: Balancing Act Pre-Lab Questions: Some handy vocabulary for you to define: Force: _____________________________________________________________________________________ Lever Arm: _____________________________________________________________________________________ Torque: _____________________________________________________________________________________ Fulcrum: _____________________________________________________________________________________ Equilibrium: _____________________________________________________________________________________ Introduction: Ever had to carry a single heavy sack of books or groceries with one hand? What happens to your body to allow you to do this? How is your body different when you have to carry TWO sacks, one on each side? Can you successfully totter with someone heavier than you? How? Many people think that weight is all that matters when you balance something but you know that downward force is only a part of the situation. Procedure: Play with the Sims  Physics  Motion  Balancing Act Take some time to play with the simulation. Go ahead. Play. Have fun. Learn. Are you still reading this? Observe the following situations below and draw your prediction of what would be needed to bring all the objects into equilibrium. Test your prediction in the simulation.

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The next few require you to do a little more math… Calculate exactly where the floating object should be placed to assure all objects are in equilibrium. Show your work below each drawing. You may check your work in the simulation AFTER calculations.

Show your work here. Remember units!

Show your work here. Remember units!

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Part 2: Torque Open rotation virtual lab: http://phet.colorado.edu/simulations/sims.php?sim=Ladybug_Revolution 1. 2. 3. 4. 5.

Set the angular velocity to 90°/sec Hit play, and notice the size of the green velocity vector and pink acceleration vector. Reset, and move the lady bug to the very edge of the platform. Set the angular velocity back to 90°/sec. What happens to the velocity vector? _________________________________________ What happens to the acceleration vector? ______________________________________

6. Use the ruler to determine the distance of the lady bug to the axis of rotation. (Assume each numbered division is a cm, not a meter). r = ___________ 7. Calculate the tangential speed v = ωr (be careful of angle units): 8. Calculate the radial acceleration: 9. What is the tangential acceleration? 10. Click the tab at the top left that says rotation 11. Set the angular velocity = 90°/sec. 12. Sketch the graph of the Angle, and the graph of Angular Velocity. (Don’t worry about numbers, just give the shape of the graph) 13. 14. 15. 16. 17. 18.

Reset all Click the third option down on the right under “Show graphs” (θ, ω, v) On the Velocity graph, click all three boxes: Show speed, show X - Vel, show Y - Vel Set the angular velocity = 90°/sec. Graph all three lines in the velocity graph What relationship can you make about the red, blue, and green lines? (Stop at any point and use the given numbers to verify your answer).

19. 20. 21. 22.

Reset all Click the second option down on the right under “Show graphs” (θ, ω, α) Set the angular acceleration = 30°/sec2. Sketch the graph of the Angle, Angular Velocity, and Angular Acceleration (Don’t worry about numbers, just give the shape of the graph)

23. Reset all 24. Click the forth option down on the right under “Show graphs” (θ, ω, a). Check “Show Acceleration.” 25. Set the angular velocity = 90°/sec. 26. Why does the acceleration remain constant despite the changing direction of the lady bug?

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