2.1. Levers.

A lever is a rigid bar that turns around a point called a fulcrum. Various forces may act on the lever at the same time.
Each force produces a specific torque, which is the force multiplied by its distance from the fulcrum.
                               Torque = Force x Distance

When the forces acting on opposite ends of a lever are equak, we say the lever is equilibrium. We can express this mathematically as the Law of the Lever.

                                       F x d = R x r

F is the force or the effor that we use; d is its distance from the fulcrum; R is the resistance or load that we want to move; and r is its distance from the fulcrum.

• Classes of levers.

We can divide levers into classes according to the location of the fulcrums, force and resistance.

Each class of lever has different uses:

• Class 2 levers increase the force that we apply.
• Class 3 levers increase the distance that the end of the lever moves.
• Class 1 levers can do both of those things.

1. A hand crank.

A crank is a Class 2 lever, so it ibeys the Law of the Lever.

                    F x d = R x r

F is the force that we apply; d is its distance from the axis of rotation.
R is the resistance in the shaft; and r is the radius of the shaft itself.