Module 3

How Does Force Affect Motion?


Student Guide


Bill Edelbrock, Eugene Judson, Terry Leyba, Jeff Turley,
Rachel Wagner


INTRODUCTION

You and your friends are completely bored, and cannot think of anything to do. Your only remaining choice to entertain yourselves is to play air hockey on a flat table top. While watching others play, the question of the motion of the puck comes to mind. (I told you you were bored!)
You begin thinking about the causes for the motion of the puck across the table, and the different kinds of motion you can give it. You wonder how you could best describe the air hockey puck's motion as it slides across the table.

Sketch a diagram showing the forces acting on the puck as it glides across the table. Discuss your force diagram with other members of your group and be able to describe and discuss your diagram in class.


OBJECTIVES

  1. To examine the relationship between force and motion.

  2. To determine a relationship between force and acceleration.

Part I: MATERIALS

dry ice, in 2-3 cm chunkslong, flat table or tile
glovesrubber bands
rulerssandpaper
tapepaper
strawsstring




Part I: PROCEDURE

  1. Obtain a piece of dry ice.
  2. Slide the chunk of dry ice around on the table top, while making observations of the ice's motion..
  3. Consider how force affects the motion of the ice. Be able to summarize and discuss your observations with the class.

Part II: MATERIALS


CartTrack
PulleyString
Hanging MassesMotion Detector
Force ProbeCBL
TI-83Motion Detector "target"

Part II: PROCEDURE:

  1. Set up CBL system as shown.



  2. Attach force probe to channel one.



  3. Attach motion detector to sonic port.








  4. Secure force detector to cart.



  5. Face motion detector toward the back end of the cart, and toward the target.



  6. Adjust string line attached to cart so that when it is pulled back and released, the hanging mass hits the floor just before the cart reaches the edge of the track.

COLLECTING DATA WITH THE TI-82/83 AND CBL:

  1. Once you have the TI-82/83 connected to the CBL turn on both the calculator and CBL. Press PRGM to view to programs stored in the calculators memory. The display should appear like the picture to the right.






  2. Use the down arrow to scroll down to the program called SECOND then press ENTER. The screen should look like the picture on the right. Press ENTER again.







  3. At the question mark type in 0 (zero) and press ENTER


  4. Distance between the cart , when pulled back ,and the motion detector should be at least 50cm.


  5. Make sure the cart /pulley assembly is set up and ready. Press ENTER and when the motion detector begins clicking release the cart.




  6. After the data is collected the display at right will appear. Arrow down to 2: FORCE-TIME and press ENTER



  7. The FORCE-TIME graph should appear on the display.




  8. If you wish to view the VELOCITY-TIME graph push PRGMand scroll down to :PLOTS and press ENTER



  9. Now go to :VELOCITY-TIME and press ENTER



  10. Consider the information available from the graphs. Discuss with your group what data should be recorded or graphed and why. Be prepared to discuss this with the class.

Analysis
 1. Examine the graphs of F vs. t, and V vs. t.

2. Determine how varying forces affects motion

3. Use a whiteboard to express the relationships you've discovered. (Graphically, Algebraically, and Verbally )

Your presnetation should include:




Application Questions:

1. Suppose a space ship is connected by a cable to a satellite, and both are moving with the same constant velocity through space far from stars and planets. What will happen, if anything, to the motion of the space ship and the satellite if the cable is suddenly cut? Explain your reasoning.

2. Why does a driver of a car have to keep his or her foot on the accelerator to maintain a constant speed?

3. Under what conditions would a car traveling down a hill in neutral gear not accelerate?

4. If you are juggling in the back of a van moving at a constant velocity, what effect will the van's acceleration have on the balls while in the air if the van were to suddenly speed up?

5. List all of the forces acting on an ice hockey puck while it is travelling at constant velocity on top of an ice surface.

6. Four motors of varying horse power are tested on four boats of similar style. Given the force-acceleration graphs below, which boat has the least mass? Explain your reasoning.




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Last modified 12 Aug 1997
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