In science, a lever is a simple machine made of a rigid beam and a fulcrum. The effort (input force) and load (output force) are applied to either end of the beam, and the fulcrum is the point on which the beam pivots. When an effort is applied to one end of the lever, a load is applied at the other end of the lever, which can move a mass upward. Levers rely on torque for their operation, which is the amount of force required to cause an object to rotate around its axis or pivot point. A lever provides mechanical advantage, which refers to how much a simple machine multiplies an applied force. The location of the effort, load, and fulcrum determines the type of lever and the amount of mechanical advantage the machine has. There are three types, or classes, of levers:
- First-class lever: The fulcrum is located between the effort and the load. Examples include a seesaw, pliers, and scissors.
- Second-class lever: The load is located between the fulcrum and the effort. Examples include a wheelbarrow, bottle opener, and nutcracker.
- Third-class lever: The effort is located between the fulcrum and the load. Examples include a shovel, fishing rod, and tweezers.
The farther the effort is away from the fulcrum, the easier it is to move the load. Mechanical advantage can be calculated using a formula that takes into account the distance from the effort to the fulcrum and the distance from the load to the fulcrum. Levers are used in many day-to-day activities and can be found in common devices such as a fork, a pair of scissors, and the handle that flushes a toilet.
