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Published byRebecca Eaton Modified over 9 years ago
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Ideas about Work and Energy What exactly is energy?
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Work We use this word in many different ways…. In physics, Work means something very specific Work = Force x distance where both Force and distance are vectors. Work = the amount of Force applied along the direction the object is moving.
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Work Work = Force x distance (mathematically this is the dot product) Work can be positive or negative. Positive work increases the energy of an object. Negative work decreases the energy of an object (think of friction on a sliding object)
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Types of energy There are many types of energy………chemical, nucular, sound, heat, etc. For now we will mainly be talking about mechanical forms of energy which include Kinetic Energy, Potential Energy, and spring energy Energy is often described as the ability to do work. It’s a method of keeping track of “stuff” because in a closed system energy is conserved. Conservation of Energy: one of the main conservation laws in science.
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Types of Mechanical energy Kinetic energy = ½ m v 2. This is the energy an object has because it is moving. Potential Energy (gravitational) = mgh. This is the energy an object has because it has height and the potential to fall.
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Conservative Forces The Potential Energy of gravity is a “conservative” form of energy. PE is path independent, it only depends on the starting and ending locations. PE is always a change in energy, meaning it has a reference point. This reference point is the location you are calling h = 0.
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Conservation of Energy If no external forces are acting, then the total energy of a system does not change. Examples of this are a 1)pendulum with no friction or air resistance 2) roller coaster with no friction or air resistance. Can determine speeds and heights based on total energy remaining constant.
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Energy problems with work If an external force is acting, then Work is done by this force. Work can either increase the starting energy or decrease it.
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