A rescue team uses a long steel rod as a lever to lift a heavy concrete slab. To minimize the force required, where should the fulcrum be positioned?
Near the slab being lifted
For a lever, load × load arm = effort × effort arm.
The effort needed falls as the effort arm grows and the load arm shrinks, so the fulcrum should be placed close to the load.
Putting the fulcrum near the slab makes the load arm very short and the effort arm almost the whole rod, giving the largest mechanical advantage; placing it midway or near the effort would need as much or more force.
Hence, the answer is near the slab being lifted.
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