Lever

A lever is a rigid bar that rotates around a fixed point called a fulcrum. It transmits force, trading distance moved for force gained.

Fulcrum: A fixed point or axis about which a lever rotates. It is the pivot that defines a lever’s motion.
Force: An interaction that changes an object's motion or shape, described by magnitude and direction. Effort and load are forces acting on the lever.
Crowbar: A metal bar used to pry, pull nails, or separate materials. Its long arm helps lift or separate loads with less effort.
First-class lever: A lever with its fulcrum between the effort and the load. This arrangement can reverse force direction and vary force advantage.
Moment (physics): The turning effect of a force about a point, equal to force times perpendicular distance. A lever balances turning effects on opposite sides of its fulcrum.
Rotation: The turning of an object around an axis or point. A lever’s defining motion is rotation around its fulcrum.
Scissors: A cutting tool made of two pivoted blades operated by handles. Each handle and blade acts as a lever around the central pivot.
Second-class lever: A lever with its load between the fulcrum and the effort. Its effort arm is longer than its load arm, giving force advantage.
Mechanical advantage: The ratio of a machine’s output force to its input force. A lever’s arm lengths determine its ideal force advantage.
Torque: A measure of how strongly a force tends to rotate an object about an axis. Torque quantifies the turning effect that governs lever balance.

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