In physics, energy is how work gets done. This video describes one important type of energy, mechanical energy, and provides examples of both kinetic and potential mechanical energy.
What Is Mechanical Energy?
Mechanical energy is the energy possessed by an object due to its motion or its position. Well, that seems simple enough, but what is energy? Energy is the ability to do work, where work is the movement of an object when a force is applied to it. For example, a person doing push-ups is doing work by applying force to the floor. Since the floor doesn't typically move, the person will move away from the floor. That same person could apply a force to a book and move it over his or her head. In each case, work is done when the applied force causes an object to move.
Let's describe mechanical energy in more detail. As I said before, mechanical energy is the energy possessed by an object due to its movement or position. In other words, an object possesses mechanical energy when it has the ability to do work due to its position or motion. Mechanical energy can take the form of either kinetic energy, which is energy due to an object's motion, or potential energy, which is stored energy due to an object's position.
Application of Mechanical Energy
Let's now look at some examples of mechanical energy. A demolition machine is a great example of both potential and kinetic mechanical energy. The wrecking ball possesses potential mechanical energy when it is raised to a vertical position above the ground. The ball has the ability to do work due to its vertical position. Now remember, work is done when a force moves an object. In the case of the wrecking ball, gravity provides the force to move the ball once it's released. Once released, the wrecking ball contains kinetic mechanical energy, as it has the ability to do work due to its movement. If the wrecking ball contacts a building, the building will move. It will fall down.
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Let's do an experiment with mechanical energy. If you are watching this video on some mobile device like your laptop, go ahead and lift it about six inches from its present position. Congratulations! You just demonstrated mechanical energy. So, don't let anyone tell you that you didn't accomplish any work today. The force generated by your muscles moved the device, and that's work. Don't overexert yourself. You can put the device back down now.
Sometimes, mechanical energy moves the object that possesses the energy. For example, the person, not the Earth, moves when the person does a push-up. I have yet to see anyone move the Earth when performing a push-up. In this case, the person moves rather than the Earth because the Earth is stationary. Similarly, the person moves when they do a chin-up. Here, the bar is stationary so the applied force due to muscle contraction moves the person and not the bar - that is, assuming the person can generate enough force to do a chin-up.
In review, mechanical energy is energy possessed by an object due to its motion or its position. Energy is the ability to do work, and work is accomplished when a force moves an object. Mechanical energy comes in two forms: kinetic energy, in which an object has the ability to do work when it moves, and potential energy, in which an object has the ability to do work due to its position. In either case, mechanical energy is the ability to do work.
You will be able to do the following after this lesson:
Define mechanical energy, energy and work and explain the relationship between the three
Differentiate between potential energy and kinetic energy and give examples of each
In this activity, students will be applying their artistic skills to draw examples of mechanical energy in action. For example, students might choose a car engine as an example of mechanical energy at work. They would draw an illustration of a car driving down the street and can include fun details, such as themselves or their family in the car. They should also write a caption explaining how the illustration shows mechanical energy. In this example, a student might write, "A car is an example of kinetic mechanical energy because the engine does work to move the car forward. In my illustration, you can see my dad driving the car to take my siblings and me to the beach!"
In this activity, you'll be creating three graphic illustrations of mechanical energy. For each one, you should choose a scenario in which kinetic or potential mechanical energy is used. Draw an illustration of the example and then include a three-sentence description of how the energy is being portrayed and additional information about the scene. To make sure your drawings have all of the required criteria, check out the criteria for success below.
Criteria For Success
Three illustrations show kinetic or potential mechanical energy
At least one example of kinetic and one example of potential mechanical energy is used
Each illustration has a three-sentence description of the scene and explains how mechanical energy is portrayed
Illustrations are colorful and professional
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