Mechanical energy, mechanical energy is the energy due to the position or movement of an object okay. And ther are 2 big forms of mechanical energy, kinetic energy and potential energy.
So let's look at some examples I've got my scush ball and if I hold it up high it's got potential energy right? I can let go of it and what happens? Well that potential energy is getting converted into kinetic energy right.
Right down here when it hits the floor it has no potential energy and I've stopped the kinetic energy right so again those types of energy are transferable and you'll often see a lot of problems where you've got to convert something from a certain amount of kinetic energy to potential energy let's say with a pendulum that's moving where it has a maximum amount of kinetic energy and then that kinetic energy is slowly converted into potential energy.
So let's look quickly at what kinetic and potential energy is. So kinetic energy which is the energy of movement equals one half times the mass of the object times the velocity squared. So one half mv squared is the formula we use for kinetic energy. Because the hammer has mechanical energy in the form of kinetic energy , it is able to do work on the nail. Mechanical energy is the ability to do work. Another example that illustrates how mechanical energy is the ability of an object to do work can be seen any evening at your local bowling alley.
The mechanical energy of a bowling ball gives the ball the ability to apply a force to a bowling pin in order to cause it to be displaced. Because the massive ball has mechanical energy in the form of kinetic energy , it is able to do work on the pin. A dart gun is still another example of how mechanical energy of an object can do work on another object.
When a dart gun is loaded and the springs are compressed, it possesses mechanical energy. The mechanical energy of the compressed springs gives the springs the ability to apply a force to the dart in order to cause it to be displaced.
Because of the springs have mechanical energy in the form of elastic potential energy , it is able to do work on the dart. A common scene in some parts of the countryside is a "wind farm. The mechanical energy of the moving air gives the air particles the ability to apply a force and cause a displacement of the blades. As the blades spin, their energy is subsequently converted into electrical energy a non-mechanical form of energy and supplied to homes and industries in order to run electrical appliances.
Because the moving wind has mechanical energy in the form of kinetic energy , it is able to do work on the blades. Once more, mechanical energy is the ability to do work. As already mentioned, the mechanical energy of an object can be the result of its motion i.
The total amount of mechanical energy is merely the sum of the potential energy and the kinetic energy. This sum is simply referred to as the total mechanical energy abbreviated TME. Assume that no energy is lost to friction. At any point in the ride, the total mechanical energy is the same, and it is equal to the energy the car had at the top of the first rise.
This is a result of the law of conservation of energy , which says that, in a closed system, total energy is conserved—that is, it is constant. Using subscripts 1 and 2 to represent initial and final energy, this law is expressed as. Either side equals the total mechanical energy. The phrase in a closed system means we are assuming no energy is lost to the surroundings due to friction and air resistance.
If we are making calculations on dense falling objects, this is a good assumption. For the roller coaster, this assumption introduces some inaccuracy to the calculation. When calculating work or energy, use units of meters for distance, newtons for force, kilograms for mass, and seconds for time. This will assure that the result is expressed in joules. Compare it to the amount of work it would take to walk to the top of the roller coaster. Ask students why they may feel tired if they had to walk or climb to the top of the roller coaster they have to use energy to exert the force required to move their bodies upwards against the force of gravity.
This video discusses conversion of PE to KE and conservation of energy. The scenario is very similar to the roller coaster and the skate park. It is also a good explanation of the energy changes studied in the snap lab.
Before showing the video, review all the equations involving kinetic and potential energy and conservation of energy. Also be sure the students have a qualitative understanding of the energy transformation taking place. Refer back to the snap lab and the simulation lab. A 10 kg rock falls from a 20 m cliff. What is the kinetic and potential energy when the rock has fallen 10 m? Substitute the known values into the equation and solve for the unknown variables.
Alternatively, conservation of energy equation could be solved for v 2 and KE 2 could be calculated. Note that m could also be eliminated. Note that we can solve many problems involving conversion between KE and PE without knowing the mass of the object in question. This is because kinetic and potential energy are both proportional to the mass of the object. Dividing both sides by m and rearranging, we have the relationship. Kinetic and potential energy are both proportional to the mass of the object.
A child slides down a playground slide. If the slide is 3 m high and the child weighs N, how much potential energy does the child have at the top of the slide? It falls to the ground, converting all of its PE to kinetic energy. What is the velocity of the apple just before it hits the ground?
You will then check your prediction. You will be dropping objects from a height. Be sure to stay a safe distance from the edge. Make sure that you do not drop objects into an area where people or vehicles pass by. Make sure that dropping objects will not cause damage. Before students begin the lab, find the nearest location where objects can be dropped safely from a height of at least 15 m. As students work through the lab, encourage lab partners to discuss their observations.
Encourage them to discuss differences in results between partners. Ask if there is any confusion about the equations they are using and whether they seem valid based on what they have already learned about mechanical energy.
Ask them to discuss the effect of air resistance and how density is related to that effect. Identify equivalent terms for stored energy and energy of motion.
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