Conceptual Physics http://mrlafazia.com/PHYS111/lessons/201011Fall/PHYS111_12.ppt THURSDAY September 30 th , 2010 LESSON GOALS : • Discuss nature of Forces • Look at history of Galileo and his contributions to Force concepts • Run Interactive Physics simulation 6.3 • Complete real-life experience discussion prompt • Review important definitions (with corresponding simulations) • Read Poem Newton Stole the Limelight • Take a quick quiz 1/19
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Conceptual Physics THURSDAY September 30 th, 2010 LESSON GOALS: Discuss nature of Forces.
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LESSON GOALS:• Discuss nature of Forces• Look at history of Galileo and his contributions to Force concepts• Run Interactive Physics simulation 6.3• Complete real-life experience discussion prompt• Review important definitions (with corresponding simulations)• Read Poem Newton Stole the Limelight• Take a quick quiz
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Discussion
• “What is a force”?– Is it a physical thing? – Are there many types? – Is there a single equation that describes forces?
• “How do forces relate to our Energy concepts”?
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Galileo Galilei on Inertiaa MrLaFazia.com original snapshot
• Imagine if a ball were allowed to roll down a ramp and roll right onto a level ramp.– Without a force to slow it down or speed it up,
what would happen to its motion?• THIS is the concept of “inertia.”
– What would be needed to speed up the ball?– What would be needed to slow down the ball?– ______________ slow down the ball in the real
world. This does NOT violate the concept of Inertia, but rather justifies it!
Frictional Forces
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The Law of Inertia
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Forces…Motion…& Energy?• Do the results of the ramp experiments (see page
32, Figure 3.4 of Conceptual Physics, if applicable) match up with our understanding of the Conservation of Energy (“Total Energy is Boring”) Principle?
• Perhaps you have heard the formation of these concepts attributed to Sir Isaac Newton or another scientist, before. There is a someday-famous poem which describes this misconception quite well. I will read it to you at the end of the class.
• “Describe an experience you have had in life where you have had the following things happen (or have caused these things to happen)” :
• Had to keep an object moving (how did you do this?)• Had to keep an object FROM moving (how did you do this?)• Had to stop an object while it was already IN motion (again,
how did you do this?)• Try to provide a name (of your own choosing) for each force
involved!
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Definitions (w/ Simulations)– Mass vs. Weight
• PLEASE learn the difference.– European scales?– American vs. European Scales on the Moon?
– support force• also known as the “normal” or “perpendicular” force
– I primarily call it the “Normal” force…just so you know.
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Poem:Newton Stole the Limelight, by D. LaFazia
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Quick Quiz“A parachutist jumps out of an airplane from the usual height (under 3
miles above the Earth’s surface). She is of average size and mass. Describe her descent in the real world (with air resistance) at the following segments of her fall”:
• What happens during the time from when she has just jumped out of the plane to just before she pulls the ripcord to deploy her ‘chute?
• In the first few moments during and after she pulls the ripcord to deploy her ‘chute, does she (choose the appropriate response)– Fall faster– Rise upward suddenly– Fall slower– Experience no change in her motion?
• Would her eventually-reached terminal velocity be more, less, or remain unchanged if she had never opened the ‘chute?
• BONUS) Describe how the parachute would respond and affect her descent if there were no air resistance.
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Recommended Reading:Sections 3.2-3.7
Sections 4.1-4.4
These sections of the text prepare you for the Force concepts from Unit 2. We will look more at the motion concepts in later
lessons within Unit 2.
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Looking Ahead:
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• Next class we will take a closer look at Force concepts by exploring Newton’s Laws of Motion.