You may have questioned how civilizations as old as ancient Egypt constructed huge structures like the pyramids, or how you can open a jar lid in your kitchen, with relative ease.
The answer typically rests in the smart use of simple machines. These simple machines form the basis for more complex machines. They help us perform work more easily by changing the amount of force or the direction of the applied force.
While simple machines are very basic, simple machines are definitely all around you every day sometimes without you knowing it or realizing it.
Understanding these machines not only helps us understand the physics behind the world around us but will also help us appreciate the simple engineered solutions of the past, present, and even future.
Let’s now take a closer look at the six classic simple machines, and find out what they are and how they help us every day!
1. Lever: the force multiplier on a pivot.
What is it? A lever is essentially a rigid bar (or sometimes a beam) that pivots about a fixed point called the fulcrum. When you apply a force (aka effort) at one point on the lever you can move a load at another point, making it easier to lift, move, or open objects.
The relative position of your fulcrum to your effort and load will determine the class of the lever. The class of lever will also identify the mechanical advantage.
Examples of Lever in your everyday life:
- Seesaw: The seesaw is a classic example of a first-class lever. The fulcrum is in between the effort (you pushing down on your side) and the load (your friend on the other side).
- Crowbar: When you pry something open with a crow bar the ground or another surface that the crow bar is resting on is your fulcrum, the point where you push is your effort, and the object you are moving is the load. This can be classified as either a first-class or second-class lever, depending on the circumstance.
- Scissors: To understand scissors, you must understand they are a pair of first-class levers working together. The pivot point the scissors are hinged at is the fulcrum.
- Bottle opener: A bottle opener is classified as a second-class lever. For a bottle opener, the fulcrum is at one end (the edge of the bottle cap), the load (the cap) is in the middle, and the effort is applied to the handle.
- Wheelbarrow: This is another example of a second-class lever. The wheel of a wheel barrow is the fulcrum, the load (what is in the wheel barrow) is in the middle, with the effort at the handles.
- Tweezers/Fishing Rod: Examples of third-class levers. The effort is between the fulcrum and the load. These levers do not multiply force but provide a greater range of motion or speed.
2. Wheel and Axle: Making Movement Easy
What is it? The wheel and axle is a wheel that is attached to a relatively small rod or shaft (the axle) so that they rotate together.
When force is applied to the wheel, the axle turns, and vice versa. This connection reduces the effort needed to move stuff or apply rotational motion significantly.
Examples of Wheels and Axle from your everyday life:
- Car wheels and steering wheel: This big steering wheel allows you to apply a small force to turn the axle, which moves the large car tires in the desired direction. Likewise, the power of the engine will apply to the axle to turn the large wheels of the car.
- Doorknob: By turning that large knob (wheel), the small spindle (axle) will be forced to retract the latch and open the door.
- Bike gears and pedal: The pedals will turn a larger gear (wheel), which will then, through a chain, drive a smaller gear on the rear wheel (axle) to advance the bike efficiently.
- Screwdriver: When you turn the handle of a screwdriver (wheel), it causes the shaft (axle) to turn to drive the screw into a surface.
- Roller skates/Skateboard: The wheels allow you to glide smoothly across a surface and therefore allow you to convert pushing a foot with a force into a linear movement in the direction intended.
3. Pulley: Raising With Less Effort
What is it? A pulley is similar to a wheel, with a groove around the rim of the wheel that is designed to accommodate a rope or cable. Pulleys are used mainly to change the direction of a force or multiply the force applied to an object, which makes the load easier to lift.
It may make things easier to differentiate fixed pulleys (which change direction) from movable pulleys (which multiply the applied force), or systems that contain combinations of both types of pulleys.
Examples of Pulley from your everyday Life:
- Flag pole: When you pull down on the rope, the fixed pulley that is above the pole changes the direction to make the flag go upwards!
- Windows (blinds/curtains): Many blind systems (and some curtains) use a pulley to raise and lower blinds and curtains with less effort!
- Cranes: Construction cranes use a bunch of hardware with a few pulleys to lift huge beams and construction materials up in the air. This means a small engine can do a lot of work.
- Elevators: Elevators use a pulley and counterweight to move the cab up and down, which looks easy.
- Weight Machines at the Gym: Many of the machines use pulleys to change the direction of the weight and create a smoother movement when you exercise. They usually “limit” your natural movement with pulleys, but this allows for better control over the exercise.
- Clothesline: Depending on how high it is, you could hoist up the clothes to hang them on a clothesline using a simple pulley, which may be easier.
4. Inclined Plane: The Simple Ramp
What is it? An inclined plane is simply a flat piece that has a slope; one end is lower or higher than the other end.
Instead of lifting an object and going against gravity, you simply push or pull the object up the incline. Although you may move the object longer, you will use less force.
Examples of inclined plane from your everyday life:
- Ramps: A wheelchair ramp, loading ramp for a truck, or ramp on a parking level; they all provide a way to move an object (or yourself) up to another height with less force than if you were to just lifted it.
- Stairs: Each step of the stair acts like a small inclined plane, and allows you
- Hills and mountains: Roads and paths constructed on hills are inclined planes, which help people and vehicles more easily move up or down a change of elevation.
- Slides (playground): Although slides are made for going down, they can also demonstrate principles of inclined plane; gravity pulls you down the slide with less direct force than if you just dropped!
- Wedge (see below): A wedge is really two inclined planes back to back.
5. Wedge: Splitting and Separating
What is it? A wedge is a simple machine that tapers to a thin edge or a point. A wedge is two inclined planes, back to back.
A wedge is driven into an object; when the wedge is driven into the object, the wedge converts the force applied to the blunt end of the wedge to a force perpendicular to the slanting sides of the wedge that can split or separate the object.
Examples of wedges in your everyday life:
- Knife: The sharp blade of a knife is a wedge. Pushing down applies force, and the wedge action separates the food.
- Axe: An axe can use a wedge to split wood. The downward force applied to the handle of the axe is then converted into a powerful outward force that can split the log/more than a upward force, applied elsewhere to the wood when the axe blade enters.
- Doorstop: A doorstop is a wedge that is driven under a door to hold the door in the open position.
- Nails: The pointy tip of a nail is the wedge. When driven in, a nail uses its wedge action to separate the wood fibers as it is driven in.
- Chisel: When used to cut, or carve, a chisel is a wedge because everything revolves around the sharp edge.
- Plow: The blade of a plow is a big wedge that splits the soil and turns it over.
6. Screw: an inclined plane in a spiral.
What is it? A screw is an inclined plane wrapped around a cylinder or cone in a spiral pattern, called threads. Screws take a rotational motion and turn it into linear motion and multiply the force.
When you turn a screw, think about what the threads actually are; the threads act as a ramp, which slowly pulls the screw (and what it is attached to) in or out.
Examples of Screw from your everyday life:
- Wood screws/bolts: wood screws and bolts are designed to fasten things together. The threads bite into the timber or bolt, thereby creating a snug fit.
- Jar lid: The threads on a jar lid and the lip of the jar are a mechanism of a screw that seals tightly when turned.
- Light bulb: The base of a light bulb has screw threads and fits into the socket, which produces a secure electrical contact.
- Bottle caps (Some): Many plastic bottle caps utilize a screw mechanism that seals the bottle.
- Corkscrew: A standard corkscrew is specifically designed to employ the mechanics of a screw to extract a cork from a bottle.
- Car jack (screws): A screw jack uses a screw to raise a car with significant weight using very little rotation, turning the torque input into a pretty big vertical lift.
How Are Simple Machines A Foundation For Innovation?
Simple machines are a foundation for any technologically innovation imaginable from the earliest human toolkits and uses to today, and will to further inspire innovation into the future.
Simple machines demonstrate some of the basic principles of physics : how force, distance, and work are related. Understand the six simple machines in this section goes a long way in explaining how so many things we use every day work and it provides you with a new perspective on the incredible creativity of human design.
Next time you see a ramp, turn a knob in a door, or open a bottle; take a moment to appreciate and realise that simple machines are at work for you, and have done the heavy lifting to make your life easier.