When two carts push apart, each pushes the other. The pushes act on different carts. With equal masses, the carts move away equally quickly. A heavier cart gains less speed from the same brief push. The two interaction forces are equal in size and opposite in direction, even when the masses differ. A brief push gives both carts equal and opposite impulses. After the push, watch them coast.
Forces, motion and energy · Discover & try
Why can equal pushes produce different motions?
Reading level 2 of 5 · DevelopingChange
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
- They coast away at equal speeds in opposite directions.
- The heavier right cart moves more slowly after the same brief push.
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 2026-10-29. Explanations and activities by Nepedia. Source links do not imply endorsement.
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