Levers trade force for distance — Physical education, 7–10 years
A lever helps move a load by turning around a fixed point. A longer handle can make the push easier, but your hand then travels farther.
A bar that turns
A lever is a stiff bar that turns around a point called a pivot. You push one part, and another part moves a load. Changing the distances from the pivot changes how easy the job feels: a long handle can give your push more turning effect.
The problem levers solve
Some loads are too heavy or stuck too firmly to move with bare hands. A lever lets a person use a smaller push over a longer movement. This does not create energy for free: the easier force is exchanged for a longer distance or a slower movement.
Lifting with a bar
Imagine a 30 kg rock 20 cm from a pivot. You press down 60 cm from the pivot, three times farther away. In a simple lever, the load-side distance is one third of yours, so a push of about 10 kg-force can balance the rock. Your end moves three times farther.
The common mistake
It is reasonable to expect a lever to make every part of a job easier. But a lever does not reduce both force and distance at once. If it makes the force smaller, you usually move your end farther, and the load may rise only a short way. The trade is the useful part.
Where we use it
A bottle opener uses a short hook and a longer handle to lift a cap. Scissors use two levers joined at a pivot, while a wheelbarrow uses its wheel as a pivot to carry a load. Pliers also use levers, changing a hand squeeze into a stronger squeeze at their jaws.
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