simple machines in your home or basement

A simple machine is a classical mechanical device that changes either the direction or the size of a force. The six simple machines are:

  • Inclined Plane

  • Wedge

  • Lever

  • Screw

  • Pulley

  • Wheel and Axle

These simple machines have been known since the Ancient Greeks, with some such as the lever and the wheel being even older. Despite their relative age, simple machines are ubiquitous in modern homes, with many everyday items being based on the principles of increasing or changing the direction of force.

Inclined PLane

An inclined plane looks, at first glance, like a ramp and nothing more. However, its applications are far greater. In effect, an inclined plane is a sloping surface, providing a tapered end that diverges from the horizontal or vertical.

An inclined plane reduces the amount of force needed to move an object up a given height, and also allows for forward motion to become vertical motion.

This combination of functions makes it perhaps the most useful (and ubiquitous) simple machine.

Gentle Slope means less force needed but more distance will be covered

Steep Slope means more force needed but shorter distance covered

Stairs

It may seem counter-intuitive, especially as an inclined plane is effectively a ramp, but stairs are actually a form of an inclined plane. Each step forward allows you to gain height with much less effort than if you were to climb.

The steeper the stairs, the shorter the distance you will need to cover, but the greater the effort. The shallower the stairs, the longer the staircase will be, but the less effort that will be required to ascend.

pipes

Ultimately, anything in a home that goes uphill or downhill is an inclined plane. All pipes in your home are therefore inclined planes since they allow for waste liquid to flow away from your home and into the sewer system.

Pipes only have a very slight decline, although the presence of that decline is what makes them into inclined planes.

The downward pull of gravity on the waste liquid is what causes it to run forwards down the pipe, thus showing the ability of a plane to convert both downward forces into lateral motion, and lateral forces into downward motion.

wedge

A wedge consists of two inclined planes, combined to create a narrow (or sharp) edge. This edge is placed onto an object and a force is applied to the broad end.

The purpose of a wedge it to allow the thrust of the input force to become a lateral output force in both directions.

Wedge

Inclined Plane

Input Force

Output Force

The lateral force produced can split apart an object; alternatively, when combined with the equal and opposite force, can hold an object in place due to the friction on the surface.

Axes

  • An ax is one of the most intuitively wedge-shaped objects in the home. An ax is effectively a wedge with a handle. They are designed to slice into a piece of wood, splitting it down its grain. Axes are prehistoric pieces of technology, still functioning in the same way as they would in the ancient world.

  • When we think of an ax ‘cutting’ a piece of wood, what we actually are seeing is a piece of wood being pushed apart by a force on the inside (hence why the pieces often fall sideways). The lateral force is equal to the downward force on the ax.

Nails

Despite nails being cylindrical, they are, in fact, wedges. Their tapered point allows them to enter a surface before the lateral force produced opens up a wider space for the shaft.

The friction on the nail then holds it in place, allowing it to carry heavy loads, effectively diverting the downward force (when hanging a painting) into lateral force in the supporting walls.

Removing a nail often requires a claw hammer, a domestic tool based on the principles of the lever.

Knives

Unlike nails, which are designed to hold things in place, knives are built to separate an object into two or more parts. The downward pressure on a knife pushes apart the two sides, allowing for an object to be cut or sliced.

Knives are extremely tapered wedges; one of the reasons why a blunt knife is less effective than a sharp one is because of the fact that the two planes are no longer inclined to the same degree.

Sharpening a knife on a whetstone rectifies this.

lever

A lever is a bar pivoted on a fulcrum. If the fulcrum is placed in the center of the bar, then the downward force is equal to the upward force (think of a see-saw).

However, by moving the fulcrum, you can change the forces produced.

The further the fulcrum from the point of downward force, the greater the upward force.

This allows for different household tools to use levers and fulcrums to create additional force and help you lift heavier loads. A prime example of this is a wheelbarrow.

The image beside shows the principles of a lever.

Balance Scale

A balance scale is based on the principles of a lever. Placing an object on one of the trays underneath a scale will cause its weight to exert a downward force. This will cause an equal and opposite upward force on the other tray.

Only by placing an object of the same weight will the two forces equal one another, and the two trays be at the same height.

If you were to move the fulcrum (or the pivot point) the scales would not function, as equal weights would not produce equal force.

Scissors

A pair of scissors actually combines the principles of a few simple machines. The blades of the scissors are wedge-shaped and have the same cutting effect as a knife.

However, the force exerted by a pair of scissors is caused by the length of the blades, and the proximity of the handles to the fulcrum.

The act of closing the pair of scissors causes the lever (the blade) to exert a force; because there are two blades, they pinch the object and then the wedges are able to separate the object into two distinct parts with lateral force.

Screw

A screw is effectively an inclined plane wrapped around a cylinder (as shown in the diagram below).

Because of the angle of the thread, the screw is able to convert torque (or rotational motion) into linear motion.

As you twist a screw, it moves further into an object.

Cylindrical shaft

Ridges(Narrow inclined plane wrapped around a cylinder)

A screw can be used either to fix two surfaces together or to hold something in place when used in conjunction with a nut.

In both cases, it is the principles of friction, and the screw’s large surface area, that holds it in place.

Corkscrew

A corkscrew, or wine bottle opener, combines the principles of a screw with those of a lever. Firstly, the screw is turned and heads vertically down into the cork. The friction, and the inability of the screw to be pulled upwards without turning, allows it to stay in place.

The levers of the handle mean that the user can apply a downward force, which then is converted into upwards effort, which raises the cork from the bottle.

This upward force overcomes the friction force holding the cork to the side of the bottle opening, thereby pulling it out of the bottle.

Light Bulbs

Lightbulbs themselves are actually complex machines.

However, the act of inserting them into a light socket often involves the principle of the screw. Unlike a traditional screw, the light bulb does not require a sharp, tapered inclined plane, but is pre-molded to fit into a groove in the light socket.

Again, the shape of the screw prevents it from being able to fall directly downwards, and it can only be removed through the application of torque.

Pulley

A pulley is a means of changing the direction of a force. In most cases, a rope is affixed around the rim of a wheel.

Pulling downwards on the rope will turn the wheel, and will cause the load to be lifted.

Load

Force

The three types of pulleys are the fixed pulley, when the axles are fixed in place; the movable pulley, where the load is attached to the pulley and both move; and the compound pulley, where a series of pulleys work together to reduce the effort required to lift the load.

Window Shades

  • Windows shades are good examples of pulleys in the home. As you pull downwards on the cord, the pulley at the top turns and the shades are raised, drawing them to the top of the window. The locking mechanism prevents them from lowering automatically, although when they do lower, the principle is based upon a pulley system.

  • Similarly, if there is a mechanism to turn the shades to allow light in, this is also based on a pulley system, and may actually have two sets of pulleys – one to allow a downward force to become lateral motion, and one to allow this lateral motion to rotate each individual shade.

Wells

Wells are thought to be some of the earliest applications of the pulley system. The need to raise a bucket of water from a height well below ground level necessitated the development of a pulley mechanism, and this system is still in use today.

Pulling down on the rope (or turning the handle, which exerts downward pressure on the rope) will cause an upward force on the load, thus raising it.

Wheel and Axle

The wheel is one of the most intuitively simple of all the simple machines. A wheel, in combination with an axle, allows for torque (rotating motion) to be converted into lateral motion.

Wheels also allow for the opposite (as in the case of a pulley). Because wheels are circles, they allow for constant motion, because the axle remains at a constant height off the ground.

Axle

Axle

Wheel

Input Force

Output Force

Wheels can operate without axles (as in the case of using a cylindrical log as a way of moving large blocks of stone), although in most cases they do have axles present, as this stabilizes them and allows for a more effective transfer of force.

cars

All cars have a wheel and axle mechanism within them. Most cars have four wheels, on two sets of axles. One set of axles provides the thrust, which comes from the engine turning a crankshaft to provide forward motion. The axles then turn, causing the wheels to turn, which moves the car.

There are additional elements to this simple machine as (at least) one of the sets of the wheels will have an additional pivot for turning, and most cars have sophisticated suspension systems that amend the wheel and axle calibration.

Broadly, however, cars function based on that principle.

Door Hinges

Door hinges, unlike cars, may not initially seem as though they use a wheel and axle. However, the wheel actually is within the axle and is a long, thin cylinder shape. The hinges allow for a door to turn on them, meaning that it takes little effort to open a door to pass through.

A door may also contain a second wheel and axle system if it has a doorknob. In addition, the door itself is a level, since the fulcrum is the hinge, and the load is at the center of the door.

Simple machines may be ancient technology, but they are far from being obsolete. In fact, with the development of ever-more technology for modern homes, there are more simple machines in every room of the house.

Knowing what constitutes a simple machine, and some of their common applications means that you will be able to look for them (and notice them) throughout your home. Although we use computer technology to a greater degree every day, there is still the need to increase force or to change force’s direction.

Simple machines are here to stay.