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183_notes:grav_and_spring_pe [2014/10/10 18:15] – caballero | 183_notes:grav_and_spring_pe [2021/03/12 02:45] (current) – [Types of Potential Energy] stumptyl |
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| Section 6.8 and 7.2 in Matter and Interactions (4th edition) |
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===== Types of Potential Energy ===== | ===== Types of Potential Energy ===== |
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[[183_notes:potential_energy|Potential energy]] is the energy associated with interactions between pairs of objects. In these notes, you will read about two particular types of potential energy: the energy associated with the gravitational interaction and the energy associated with a spring-mass system. | [[183_notes:potential_energy|Potential energy]] is the energy associated with interactions between pairs of objects. **In these notes, you will read about two particular types of potential energy: the energy associated with the gravitational interaction and the energy associated with a spring-mass system.** |
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==== (Near Earth) Gravitational Potential Energy ==== | ==== (Near Earth) Gravitational Potential Energy ==== |
[{{ 183_notes:potential_energy.006.png?400|A spring-mass system (spring constant, ks) is stretched through a distance (Δs).}}] | [{{ 183_notes:potential_energy.006.png?400|A spring-mass system (spring constant, ks) is stretched through a distance (Δs).}}] |
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To determine the potential energy associated with a spring-mass system, consider the work done by a spring on an object (mass, m) attached to its end. The spring is stretched through a displacement (Δ→s). The displacement and the gravitational force are in opposite directions. | To determine the potential energy associated with a spring-mass system, consider the work done by a spring on an object (mass, m) attached to its end. The spring is stretched through a displacement (Δ→s). The displacement and the spring force are in opposite directions. |
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To calculate the work that the spring does, consider the object as the system. Remember that the [[183_notes:springmotion|spring force changes with displacement]], and thus we must use the [[183_notes:work_by_nc_forces|integral formulation to calculate the work]]. | To calculate the work that the spring does, consider the object as the system. Remember that the [[183_notes:springmotion|spring force changes with displacement]], and thus we must use the [[183_notes:work_by_nc_forces|integral formulation to calculate the work]]. |
Ws=−12ks(s2f−s2i)
| Ws=−12ks(s2f−s2i)
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If you include the spring in your system, so that the system is now the spring and the object, then potential energy shared spring-object system is given by, | If you include the spring in your system, so that the system is now the spring and the object, then the potential energy shared between the spring-object system is given by, |
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- System: object+spring; Surroundings: Nothing | - System: object+spring; Surroundings: Nothing |
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Dissipative forces such as friction and air drag are non-conservative forces. The path that an object takes matters very much when non-conservative forces are present. Moreover, these dissipative forces cannot be associated with any construct like potential energy. | Dissipative forces such as friction and air drag are non-conservative forces. The path that an object takes matters very much when non-conservative forces are present. Moreover, these dissipative forces cannot be associated with any construct like potential energy. |
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| ==== Examples ==== |
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| * [[183_notes:examples:sledding|Sledding down a hill]] |
| * [[183_notes:examples:the_jumper|The Jumper]] |