How Does a Fulcrum Work?
A fulcrum is the fixed support or pivot point for a lever, which is a simple machine used to overcome resistance. The lever is a stiff rod or bar, and the location of the fulcrum determines the class of the lever. Levers are useful to increase force, increase speed or change direction of a force, according to HowStuffWorks.
In a first-class lever, the location of the fulcrum is between the load and the resistance. A seesaw is a first-class lever. The weight of one person provides the force to lift the second. Moving the location of the fulcrum toward the heavier person helps to balance the force.
The load is between the fulcrum and the force in a second-class lever, as with a wheelbarrow. While wheelbarrows combine two simple machines, the wheel and lever, the axle of the wheel remains the fixed point for the lever. Increasing the length of the handles on the wheelbarrow increases the user's mechanical advantage, so he is able to lift a larger load with less force.
With a third-class lever, the user applies force between the fulcrum and the resistance. A broom is a third class lever. The upper hand on the broom becomes the fulcrum, and the opposite hand applies a force at the middle of the broom handle. As a result, the speed of the head of the broom increases to perform the sweeping motion.