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.
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, (S)he can swim across 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
| frame of reference | Ground | Person | River | Boat |
| Object color code | Gray | Blue | dark Green | Red |
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? Fill in the chart below:
| frame of reference | Ground | Person | River | Boat | |
| Vector Color Code (Arrow Color) | Black |
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.
Observation #1