Unit Summary 5
Work and Power
Work is the principle that when applying a force over a distance one uses energy, thus working. To be doing work the distance and the force must be parallel, no work can be done if the distance and the force are not parallel. Work is measured in Jewels and is a form of energy. The formula is Work=force*distance. No matter how fast the work is done over the same distance the work stays the same. Power is the amount of work done over an amount of time and it is measured in watts. The formula is Power=work/time and 746 watts are equal to 1 horsepower.
Kinetic Energy is the energy that causes something to move and it is measured in Jewels the same as work. The change in Kinetic Energy (KE) is equal to work, the formula is ΔKE=KEinitial-KEfinal and the formula to find Kinetic Energy is KE=1/2mv^2.
Conservation of Energy
The KE is the energy of a moving object, but when the object is not moving it also has energy, Potential Energy (PE). This is the measure of if the object began to move how much KE it would have. When an object is moving it has KE and also PE as these two types of energy transfer back and forth to each other. When an object is at rest it has 0 KE and 1000 PE, once it begins to move it has 800 PE and 200 KE and as the object speeds up the KE increases as well until the KE is 1000 and the PE is 0. There can never be more energy in a system than it starts with, in the case before the PE or KE cannot exceed 1000 because it started with 1000 units of energy, this is stated in the law of conservation of energy where the Energybefore=Energyafter.
A machine, like a ramp changes the distribution of energy. Instead of having to lift a box up a meter in one go, one can push the box 4 meters with less force. The ramp increases the distance, but keeps the same amount of work because the box is still being moved up 1 meter, but over a longer horizontal distance. The single burst of energy needed to lift the box that meter is displaced over the distance of 4 meters at a constant or intervened rate. These are labeled work in and work out, the work in is the side with the longer distance while the work out is the side with the shorter distance.