Relative Motion                                                      Name ________________Period_____

A look at "Frames of Reference"
http://physci.kennesaw.edu/javamirror/ntnujava/relativeVelocity/relativeVelocity.html
 
Introduction
An object may appear to have one motion to one observer and a different motion to a second observer, depending on how the two observers are moving with respect to one another.
The object that is the frame of reference has a velocity of 0.0 m/s

This java applet let you view objects from different frames of reference.
Imaging there is a river in the center of the screen (yellow dots are moving with water - green area) a red boat is also moving with respect to the river. There is a person (blue) walking close to one side of the river.
You can easily change frame of reference by moving your mouse to different regions. 
                 e.g. If you move your mouse within the river, YOU will become an observer moving with water.
                       If you move your mouse into the boat region, You are on the boat (boat is your frame of reference and the boat appears to you to be at rest!) watching other objects that have motion.
                      The object that is the frame of reference has a velocity of 0.0 m/s.

Frame of Reference Chart
Click on the Info box at the top of the Applet.   Place your mouse arrow on the ground and click your right mouse button.  Determine the relative speed of the man, river, and boat.  Record these values in the data table.  Negative values indicates the direction is upstream.
Observation #1 Frame of Reference is the GROUND

Observation #2 Frame of Reference is the PERSON
Place your mouse arrow on the person and click your right mouse button.

Observation #3 Frame of Reference is the RIVER
Place your mouse arrow on the river and click your right mouse button.

Observation #2 Frame of Reference is the BOAT
Place your mouse arrow on the boat and click your right mouse button.

Frame of Reference 
Ground
Person
River
Boat
Ground
0 m/s
 
 
 
Person
 
0 m/s
 
 
River 
 
 
0 m/s
 
Boat
 
 
 
0 m/s
 
Program Note:
 You can press the mouse button to suspend the animation.
 If you press with left mouse button, animation will resume when you release it.
 If you press with right mouse button, you need to click it again to resume animation.
The velocity vector arrows shown do not remain the same colors.  When the ground is the frame of reference the vector arrow is BLACK.  What arrow color is used for the other frames of reference?

 ANALYSIS
1.   How much velocity change (DV) occurred to the ground, man, river and boat when the frame of reference was switched from the ground to the river? DV =  ______________
2.  What factor determines the velocity (speed and direction) measured of an object?
 
 
 

3.  When stating the speed of an object on earth, what is the frame of reference commonly used by observers?  ___________________________________
 

4.  The speed of the boat is not the same from each frame of reference.  True or False?

5.  From what frame(s) of reference is the boat stationary?  __________________________

6.  From what frame of reference(s) is the boat moving with negative velocity? ______________________________________________________________________________

7.  From what frame of reference(s) is the boat moving with positive velocity? ______________________________________________________________________________

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tranform to web page by Fu-Kwun Hwang
last modified date: 05/14/2001 18:59:54