Physics High Logo

Physics High

Frames of Reference & Relative Motion Lab

Frame: Bank Observer
Top-Down Vector Viewport (Click characters directly to switch frames)
Boat Velocity
Swimmer Velocity
Water Velocity
Bank Velocity
Live Transform Matrix (Velocity Components Relative to Chosen Frame)
Observer / Entity Horizontal (Vx) Vertical (Vy) Net Speed
Bank Observer 0.00 m/s 0.00 m/s 0.00 m/s
Boat Observer 0.00 m/s 0.00 m/s 0.00 m/s
Swimmer Observer 0.00 m/s 0.00 m/s 0.00 m/s
River Water Flow 0.00 m/s 0.00 m/s 0.00 m/s

1. Choose Frame of Reference

2. Adjust Motion Velocities

River Speed (Downwards) 1.50 m/s
Boat Motor Speed (Relative to Water) 3.50 m/s
Net velocity in Bank Frame = Boat Engine Speed minus River Current Speed.
Swimming Speed (Relative to Water) 1.20 m/s
Display Options:

What to Notice

  • In the Swimmer's Frame, the water moves completely horizontally to the left or right, because the swimmer is drifting downward at the exact velocity of the river current!
  • If you reduce the Boat Motor Speed below the River Speed, notice how the boat flows backwards (downwards) in the Bank Frame, but still travels upwards in the Water Frame.
  • The relative velocity vector of any object is equal to its own absolute velocity minus the absolute velocity of the selected frame of reference.