One of the first things you want your students to know about any topic is why it is important. If you are teaching your students about simple machines, they need to understand how important simple machines are to our lives. They need to know, how do simple machines help us?
A force is a push or a pull. There are many types of force, including friction, gravitational, electric, buoyant, spring, tensional, magnetic, and applied. When a force moves an object across a distance, work is done. For example, you are doing work when you push a box across a room.
You can exert a force without moving anything. For example, you can pull on a rope during a game of tug-o-war. If nothing moves, you are not doing work, but if the other team falls forward, then you have done work.
Work is the connection between force and energy in physics. By helping our students understand work, we are helping them get a fuller picture of the world and understand how do simple machines help us.
To understand work, students need to know that work is the product of force and distance, which means students need to understand force. Older students will need to use trigonometry to calculate work when some force is not parallel to the direction of motion. Still, if younger students can simply understand the concept, they will be set up for success later.
Students also need to know that work is a change in energy, so they need to know about kinetic and potential energy to understand how do simple machines help us.
Using Examples and Counterexamples to Teach Work
Work is a topic that requires examples. Students need to see examples of work being done and counterexamples of work not being done despite a force or a distance. Remember, force is mass times acceleration, so an object moving at a constant velocity without friction has no force, and no work would be done on it.
Power is the rate of work. Once students understand work, power should be easier to understand. Simple machines make work easier by increasing distance and decreasing force. That is the key point in learning how do simple machines help us.
How Do Simple Machines Help Us?
Simple machines make work easier. Simple machines do not change the amount of work it takes to move an object, but they decrease the amount of force necessary to do the work by increasing the distance the object travels.
Remember, work is a product of force and distance, so increasing the distance decreases the force.
Simple machines do work in a single motion. Multiple simple machines can be combined into a compound machine to perform more complex tasks. Scientists have fun putting many simple machines together to complete a task. These compound machines are called Rube Goldberg Machines after the American cartoonist who first drew the needlessly complicated machines.
The Inclined Plane
The inclined plane makes lifting objects easier by increasing the distance the object travels. Instead of lifting a wheelbarrow straight up, a person can push the wheelbarrow up an inclined plane to raise it the same distance.
The wheelbarrow ends up in the same position, so the same amount of work is done, but the distance has increased, and the force has decreased. The inclined plane makes it easier for people to lift heavy objects. That is one answer to the question, how do simple machines help us.
The wedge is a portable inclined plane. A wedge can be used to split something, like an ax splitting a log. A wedge can also be used to stop an object, like a doorstop. Finally, a wedge can lift an object, such as a plow lifting soil off the ground.
Like other simple machines, a wedge decreases the force needed to do work by increasing the distance over which the work happens.
A wedge can also change the direction of force, making it easier to do the work. When an ax splits a log, you apply a downward force, but the log’s sides move outward. Pushing down on the wood is easier than pulling it apart. That is one answer to the question, how do simple machines help us.
A screw is an inclined plane wrapped around a pole. Turning the screw can move objects up the inclined plane. Screws are also used to hold objects together.
Examples of screws include jar lids, bolts, drill bits, light bulbs, water faucets, and the ends of hoses.
Like other simple machines, screws decrease the amount of force needed to do work by increasing distance. A screw takes less force to push into a wall than a nail because the edges of the screw are moving in a circle and traveling a longer distance than the nail. That is one answer to the question, how do simple machines help us.
Screws are also helpful because the inclined plane’s edges hold the screw in place and can hold things together.
A lever is a rigid bar and a fulcrum. The fulcrum is also called the pivot point. You can apply force to one side of the lever to move an object on the other side of the lever.
There are three parts of a lever, the effort, the load, and the fulcrum. The effort is the place you apply force, the load is the object you are moving, and the fulcrum is the pivot point between the effort and the load. Levers are classified based on the location of the three parts.
First class levers have the fulcrum between the effort and the load. A teeter-totter is an example of a first class lever.
Second class levers have the load between the effort and the fulcrum. A wheelbarrow is a second class lever. The wheels of the wheelbarrow are the fulcrum of the lever. That is one answer to the question, how do simple machines help us.
The pulley is a rope looped over a wheel to make lifting an object easier. Pulleys make lifting easier in two ways. First, they change the direction of the force. Instead of pulling up on an object, you can pull down on the rope to lift it. Second, by adding wheels to the pulley, you can increase the rope’s distance and decrease the force needed to lift the object.
Lifting an object with a pulley with one wheel will change the direction of the force, but it won’t change the amount of force needed to lift the object. Using a pulley with two wheels both changes the direction of the force and cuts the amount of force needed to lift the object in half. Instead of taking 500 N to lift an object, it will take 250 N. As you add wheels to the pulley, the force continues to decrease. That is one answer to the question, how do simple machines help us.
The Wheel and Axle
The wheel and axle are a large wheel attached to a smaller rod called an axle. The larger wheel takes less force to turn because the wheel travels around a longer distance than the axle.
A screwdriver is an example of a wheel and axle. The screwdriver handle is larger than the end of the screwdriver, so it is easier to turn. That is one answer to the question, how do simple machines help us.
Teaching How Do Simple Machines Help Us
You can give your students all the relevant information about work, power, and how do simple machines help us with my latest digital science unit. Check out the pages!
Look interesting? You can get this digital science unit here.
ARE YOU TEACHING ANOTHER SCIENCE TOPIC?
I am working on creating more science units so that every science teacher can get exactly what he or she needs for her students. You can also read about how I use brain science to teach other science topics on my blog. Click the pictures below to learn more.