The activity represents a brief equal-and-opposite impulse. Impulse is force accumulated over time and changes momentum. Starting from rest, the carts gain opposite momenta of equal magnitude. Their speeds can differ because momentum is mass multiplied by velocity, so the lighter cart recoils faster.
Forces, motion and energy · Discover & try
Why can equal pushes produce different motions?
Reading level 3 of 5 · IndependentChange
Word help
Interaction pair
Equal and opposite forces acting on two different objects.
Impulse
The accumulated effect of force over time, changing momentum.
Momentum
Mass multiplied by velocity.
Watch · Try · Explain
See how it works
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Ideal two-cart recoil after a selected impulse, with no external horizontal force.
What to look for
- Identify which cart each force acts on.
- Compare opposite momenta with unequal speeds.
- Change one mass without changing impulse.
Explain what you noticed
Two different skaters push apart, one with twice the other’s mass. Which statement fits the ideal interaction?
Keep this idea: Interaction forces are equal and opposite on different objects; different masses can accelerate differently.
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Source material checked 2026-10-28. Explanations and activities by Nepedia. Source links do not imply endorsement.
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