In a world that has been propelled into progress by the development of technology, we find ourselves surrounded by machines all the time. From cars and lamps to doorknobs and pencils, we are sure to find machines wherever we go. We can even find machines in our own bodies. And, no, I don’t mean to tell you that you’ve actually been a robot this whole time. But machines can show up in many different places and ways.
Before we go any further, we should probably define what a machine is. Here’s one definition right from the dictionary: A machine is an apparatus using or applying mechanical power and having several parts, each with a definite function and together performing a particular task. That’s a mouthful. Here’s another one: A machine is a mechanically, electrically, or electronically operated device for performing a task. That’s a little better and probably the definition that you’re more used to seeing. How about this one: A machine is any device that makes work easier by changing a force. That one seems a lot more digestible. So which one is right? The answer: all of them. To understand each of them, we first need to go over a few important concepts.
Humans created tools and machines to make work require less effort. Even the earliest humans used primitive tools like sharpened rocks and sticks for hammering and hunting. These simple tools didn’t reduce the amount of work to be done but they made the work easier. For our purposes, we’ll define work as any activity that expends energy. Pretty much any machine you can think of is made up of smaller machines called simple machines. Simple machines are devices with few or no moving parts used to modify motion and force so that work can be performed with less effort. There are several types of simple machines that we will go over.
The first is the lever. Levers are simple machines that are constructed of a fulcrum and a beam. There are 3 classes of levers: 1st class, 2nd class, and 3rd class.
In first-class levers, the fulcrum is between where the effort is being applied and the load. An example of this kind of lever would be a see-saw.
In a second class lever, the load is between the effort and the fulcrum. For example, in a wheelbarrow, the load is between the handlebars where the effort is applied and the wheel.
In third class levers, the effort is between the load and the fulcrum. When you use a hammer, you hold the hammer by the handle and the load is the head of the hammer. You create a fulcrum as the bottom of the hammer when you swing it back and forth.
Levers modify the direction of the force we need to apply to accomplish a task. Say you need to lift a heavy box onto a ledge. Instead of lifting the heavy box over your head and tossing it up there, you might want to put it on a lever and push down on the other end to lift the box up. You might even drop another heavy object on the other end to apply the force you need.
Another type of simple machine is the wedge. Wedges are simple machines that are thick on one end and taper to a thin edge. They are used to split things and hold things together. The longer and thinner a wedge is, the more work it does with less effort. When effort is applied downward on the wedge, it changes the direction of the force so that the output is a diagonal force. This is how the wedge modifies the direction of force applied. Examples of wedges are axes, nails, and doorstops. You might notice that an ax can also be thought of as a lever when it is being swung.
A wheel and axle together are another type of simple machine. As the name suggests, it is made up of a circular wheel and a rod on which it turns. Force can be applied in two ways: to the wheel or to the axle. When force is applied to the wheel, the axle is turned like in the case of a doorknob. When force is applied to the axle, the wheel is turned like in the case of a vehicle's wheels. In a way, the wheel and axle are similar to a class one lever. Effort applied on the axle will cause the wheel to turn which is the output. The fulcrum lies where the wheel meets the axle.
Pulleys are simple machines made up of wheels, axles, and rope, or some other cord. Pulleys are usually used to lift objects by changing the direction of the force. There are three types of pulleys. The fixed pulley is the simplest of the three types. Its axle is fixed, meaning it can't move. The rope moves but not the wheel and axle. An example would be a flag pole. In the movable pulley, one end of the rope is fixed while the wheel and axle can move around. An example is a construction crane. The compound pulley is made up of several pulleys that each make the work easier. Depending on the type of work to be completed, you would have to figure out what kind of pulley system would be the most efficient.
An inclined plane, or ramp, is simply a sloping surface that is used for moving objects. The steeper the ramp, the more effort is required to move the object. But, when the ramp is less steep, it needs to be longer to move the object the same distance as a steeper ramp. Examples include slides, skate ramps, and wheelchair ramps.
The last of the simple machines is the screw. A screw is an inclined plane winded around a cylinder. The winding ramp is called the thread and it wraps around the shaft. The distance between the threads is called the pitch. Some examples of the screw(other than the most obvious) include drill bits, bolts, and spiraling staircases, among others. Screws are used to holding things together, tighten things, and lift heavy objects. If you think about a spiral staircase, its screw shape allows for more stairs in a small space where you may be able to put an ordinary staircase because it would be too long.
By putting these simple machines together, we can create larger, more complex machines that can accomplish more difficult tasks. Compound machines are machines made up of several simple machines. You can see simple and compound machines being used in virtually every aspect of your life. With your new knowledge of machines, you can identify them and put them to work. Of course, there’s always more to learn about machines and their role in the world around us.
References:
Let's Talk Science. “Simple Machines - Levers.” Let's Talk Science, 9 Mar. 2020,
letstalkscience.ca/educational-resources/backgrounders/simple-machines-levers.Rachelle, et
Al.
The Editors of Encyclopaedia Britannica. “Simple Machine.” Encyclopædia Britannica,
Encyclopædia Britannica, Inc., 4 Feb. 2020, www.britannica.com/technology/simplemachine.
Written by: Mahathi Somula
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