Two Cars — Same Direction

The blue car sees the orange car approach more slowly than a roadside observer does.

Tap either object to make it your reference frame. Drag to pan; wheel to zoom.

Relative Velocity Lab

Change the observer and watch measured motion transform.

Real-world example

Reference frame

18.0vA m/s

12.0vB m/s

−6.0vB relative A

vB relative A = vB − vA = −6.0 m/s

Negative means B moves toward the left in A's frame.

Object A ground velocity18.0 m/s

Object B ground velocity12.0 m/s

Starting separation80 m

Simulation speed1×

Line slope is velocity in the selected frame. Where lines cross, the objects meet.

Teacher / Demo mode

Velocities must use the same positive direction before subtraction.

Right is positive in this lab. Left-moving objects have negative velocity.

velocity of B relative to A = vB − vA

The observer's own velocity is removed from every object's ground velocity.

If relative velocity points toward the other object, separation shrinks.

meeting time = separation / closing speed

Switching to an observer moving at velocity vo changes every measured velocity by the same amount.

v in observer frame = v on ground − vo

Give both cars the same velocity: they appear stationary to each other.
Set equal and opposite velocities: closing speed becomes the sum of their speeds.
Stand on the walkway and compare a walking passenger with the terminal floor.
Switch frames while objects meet; the event itself does not change.

Score: 0 / 7