A lever balances when the turning effect on one side equals the turning effect on the other. The turning effect (moment) is force × distance from the fulcrum. So load × load distance = effort × effort distance. This is why a heavier child must sit closer to the middle of a seesaw, and why pushing far from the fulcrum of a crowbar lets a small force lift a heavy rock. To find a missing value, work out the side you know, then divide.
Missing value = the known side’s product ÷ the other number on its own side.
Use it for: Seesaw puzzles, science lessons on moments and using a crowbar or a long spanner sensibly.
Worked example: ⚖️ A lever bar balances. The load is ? N at 30 cm from the fulcrum. The effort is 120 N at 50 cm from the fulcrum on the other side. What is the missing force in newtons? → 200
Work it out in your head or on paper, then tap your answer — or type it and press Check. Stuck? Press “Show me how”.
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