A force is a push or a pull. Helpers pull ropes attached to one trolley. Two helpers on the right pull harder than one on the left, so the trolley speeds up right. One helper on each side makes equal teams. Their pulls balance. A still trolley then stays still; a trolley that is already rolling keeps the same speed. Try all three tests.
Forces, motion and energy · Discover & try
Can balanced forces act on a moving object?
Reading level 1 of 5 · EarlyChange
Word help
Net force
The combined force after directions are taken into account. Here, equal left and right pushes cancel.
Velocity
Speed together with direction. A constant velocity means that neither changes.
Acceleration
A change in velocity over time: speeding up, slowing down or changing direction.
Watch · Try · Explain
See how it works
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One 2 kg trolley, two opposing pulls and the same ruler in every test. Friction is excluded.
What to look for
- Which side has the stronger pull? Follow the arrows on the same trolley.
- Compare equal pulls with the trolley still, then already rolling. Does its speed change?
- Watch one-second position marks: equal gaps mean constant speed; growing gaps show speeding up.
Explain what you noticed
A different cart moves right while experiencing 5 N left and 5 N right, with no other horizontal force. What happens next?
Keep this idea: Balanced pulls do not change motion: a still trolley stays still, and a rolling trolley keeps the same speed and direction.
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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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