MODULE 01 / CLASSICAL MECHANICS
Newton’s Laws
Discover how forces shape the way things move.
THE THIRD LAW
One interaction. Two forces.
Equal and opposite forces act on different objects.
Learning objective
Initial conditions
Spring release · two carts
ReadyHorizontal force arrows share one scale. Equal lengths mean equal magnitudes.
Time 0.00 s · Ready
Build the Free-Body Diagram
DIFFERENT OBJECTSVerified diagrams · revealed after checking. Arrows show current simulation forces, not your proposed selections.
Each diagram contains only forces acting on its labeled cart. Horizontal arrow length = 75 SVG units × current force magnitude / initial spring-force magnitude, the same scale for A and B. Vertical arrows are schematic; numeric labels give their magnitudes. Equal interaction forces can produce different accelerations because a = F/m.
T3 focus: build each cart’s diagram, then identify the force pair across the two objects.
Compare both diagrams: identify the Third Law pair
Explore the data
| Measurement | Cart A | Cart B |
|---|
Observe for 6 s or until either cart’s outer edge reaches −50 or +50 m. Both carts then freeze at that measurement; no collision is modeled.
Synchronized interaction graphs
Graphs appear when the experiment starts.
Reflect on the evidence
Your explanation is not automatically graded or saved.
Ideal massless spring coupling: the interaction is transmitted between the carts with no momentum stored in the spring. Labels “B on A” and “A on B” refer to this effective two-body interaction. A real spring with appreciable mass would require its own force and momentum accounting. Both carts start at rest; the track is frictionless.