NSTA Web Seminar: Force and Motion: Stop Faking It!

Transcription

1 LIVE INTERACTIVE YOUR DESKTOP NSTA Web Seminar: Force and Motion: Stop Faking It! Thursday, January 15, 2009

2 Force and Motion Circular motion Different frames of reference Gravitational forces Orbiting things

3 Circular motion

4 In order to make an object go in a circle, you must exert a force Toward the center of the circle Along the circular path Both toward the center of the circle and along the circular path Both toward the center of the circle and away from the center of the circle Use your clip art to respond

5 You have a string tied to an object. In which direction(s) can you exert a force on the object using the string?

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8 You have a string tied to an object. In which direction(s) can you exert a force on the object using the string?

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10 In order to make an object go in a circle, you must exert a force Toward the center of the circle Along the circular path Both toward the center of the circle and along the circular path Both toward the center of the circle and away from the center of the circle Use your clip art to respond

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12 Centripetal force is... A special force of unknown origin that pushes things toward the center of a circular path A special force of unknown origin that pushes things away from the center of a circular path A name given to forces that are already present and causing something to move in a circle Use your clip art to respond

13 Let s Pause for Two Questions from the Audience

14 Different frames of reference

15 As a car rounds a sharp curve, you slide to one side because you re not wearing your seatbelt.

16 What caused you to slide to the side of the car? The car turned a corner but you continued to move in a straight line A centrifugal force pushed you to the side of the car The view is better next to the window Use your clip art to respond

17 It depends on your frame of reference. Here s the situation as viewed from outside the car:

18 When viewed from inside the car, there is a centrifugal force that pushes you away from the center of the circular path the car is taking.

19 Which of the following are true? Centrifugal forces aren t real. That s why they are often called fictitious forces. Centrifugal forces only show up when your frame of reference is rotating. There is no such thing as a centrifugal force. You should never talk about them. Centrifugal forces are as real as the force of gravity. Use your clip art to respond

20 A spin and barf ride as seen from outside the ride:

21 A spin and barf ride as seen from inside the ride:

22 Let s Pause for Two Questions from the Audience

23 Gravitational forces

24 F grav = Gm 1 m 2 r 2 24

25 Science Simulation from Gravity and Orbits Science Object 25

26 Weight is: The gravitational force the Earth exerts on an object The gravitational force any object exerts on another object The same as mass, but with different units Use your clip art to respond

27 Is it possible to be weightless in outer space? Yes No Depends on your frame of reference Use your clip art to respond

28 It can seem to you that you are weightless when in orbit Earth

29 You can create your own gravity in space

30 Let s Pause for Two Questions from the Audience

31 Orbiting things

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33 Which drawing shows the forces acting on the Earth as it orbits the sun?

34 Thank you! Let s Pause for Two Questions from the Audience

35 Thanks to our presenter, Dr. Bill Robertson, and to NSTA Press for sponsoring this program

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38 NASA: Discover the Universe From Galileo to Today January 20,2009 The NSTA Learning Center - Focus on Teachers January, 21, 2009 Picture-Perfect Science Lessons: Using Children s Books to Guide Inquiry, Grades K-4 January 22,

39 National Science Teachers Association Dr. Francis Q. Eberle, Executive Director Zipporah Miller, Associate Executive Director Conferences and Programs Al Byers, Assistant Executive Director e-learning NSTA Web Seminars Paul Tingler, Director Jeff Layman, Technical Coordinator LIVE INTERACTIVE YOUR DESKTOP