Simple Machines: Levers, Classes and Forces

Simple Machines and Forces: Levers, Classes of Levers, and Force Measurement

Simple machines are mechanical devices that make it easier to perform work by reducing the amount of force required. They consist of various parts such as pulleys, wheels and axles, inclined planes, wedges, and screws. One type of simple machine is the lever, which is a rigid bar used to apply force to an object. Levers can amplify or reduce the effect of applied forces, depending on their design and how they are used. In this article, we will discuss levers, classes of levers, and force measurement related to these machines.

Levers

A lever is a simple machine that consists of a fixed point called a pivot or fulcrum, and two ends connected by a bar. It allows an input force to produce output force that is proportional to the ratio of the lengths of the respective perpendicular lines from the point of application of the input force to the fulcrum. There are three types of levers classified based on the position of the fulcrum relative to the effort and load:

Type I – First Class Lever

The fulcrum is located between the effort and the load. Examples include scissors, pliers, and wheelbarrows.

Type II – Second Class Lever

The effort is closer to the fulcrum than the load. Examples include crowbars, seesaws, and nutcrackers.

Type III – Third Class Lever

The load is closer to the fulcrum than the effort. Examples include shovels, bicycle pedals, and doorknobs.

Classes of Levers

Levers come in four different classes, named after their corresponding third-class lever, based on the positions of the effort, load, and fulcrum:

Class 1 - Fulcrum Between Effort and Load

In this case, the fulcrum lies between the effort and the load. This class represents all rigid rods and does not form any lever because there is no distinction between the effort and the load.

Class 2 - Fulcrum Closer to the Load Than to the Effort

This class includes levers where the fulcrum is closer to the load than to the effort. These levers require more force to lift an equal weight than do first-class levers.

Class 3 - Fulcrum Nearer to the Effort Than to the Load

Class 3 levers have the fulcrum nearer the effort than the load. Such levers are capable of lifting heavier weights with less force, making them useful tools for moving heavy objects.

Class 4 - Fixed Centre of Effort and Load

These levers have a fixed centre of effort and load. Common examples include cables and chains.

Force Measurement

Measuring the force exerted by a lever involves calculating the efforts needed to maintain equilibrium. For example, a simple second-class lever requires a force that varies directly with the torque, which itself varies inversely with the distance from the fulcrum. To measure the force, you would need to know the moment arm, which is the length of the lever between the effort and the axis around which the rotation occurs. By multiplying the force by the distance between the fulcrum and the rotational axis, you can calculate the moment of force, which provides information about the force's magnitude and direction. This calculation helps determine whether a lever has enough strength to perform its intended task effectively.