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19 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Work |
(Scalar ) the result of a force exerted over a distance as an object moves . If an object does not move, no work is done!!! Measures in a joules(j) Generally W= Fapplied • displacement. Net work = Fnet • displacement . |
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Energy |
The ability to do work. Measures in joules (j). Comes in different forms.. Mechanical , thermal, kinetic ,electrical, light , ect.. |
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Law of conservation of energy |
Energy cannot be created or destroy , only transferred from one form to another . |
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Mechanical energy |
Sum of potential and kinetic energy in a system Em= Ep+Ek |
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Potential energy |
Energy of an object because of its position depends on force acting on object and displacement/position of the object . Ep= Fd |
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Gravitational potential energy |
Potential energy of an object due to its position above the earths surface. Depend on the reference point chosen! Ep=Fd Ep=mgh |
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When lifting in object at a constant velocity |
-work done = change in gravitational potential energy. Fnet =0N Fnet= Fapplied + Fg Fapplied =-Fg W=Fapplied = -Fgd = -mgh |
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Elastic potential energy |
Energy stored when an objects shape is changed from it's standard shape without being permanently deformed. |
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Hooks law |
Stretch produced by a force applied to a spring is proportional to the magnitude of the force. Applies to any elastic substance when a force is exerted upon it. |
F=Kx Fax |
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Potential energy of a spring |
Ep =1/2kx2 |
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Kinetic energy |
Ek= 1/2mv2 |
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Work energy theorem |
The net work dome on an object is equal to its change in kinetic energy . W net=EK Since net work is a product of the net force and displacement. Fnet d= Ekf-Eke Fnet d=1/2mv2 -1/2mv2 Want to change kinetic , imcrease neforce or imcrease distance over which the force acts (ex.follow through, crumple zone) . |
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Isolated system |
Group of objects completely isolated from all objects outside the system . No matter or energy enters or leaves the system . No force from outside the system may work to transfer any energy to form any object inside the system . |
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Conservative forces |
When work is done against a conservative force, the energy expended in doing the work is stored and recoverable . |
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Non-conservative forces |
When work is done against a non-conservative force, the expended energy is not recoverable . But is converted to thermal energy . |
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Law of conservation of mechanical energy no friction |
Em= Ep+ Ek For an object moving in a frictionless system mechanical energy is conserved . Em(before) = Em (after) If the only forces acting on an object are conservative forces the mechanical remains constant . |
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Law of conservation of mechanical energy with friction |
In reality ,no energy transformation is 100% efficient!! Energy lost is considered work done by friction . |
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Power |
Rate at which work is done Measures in Watts (w)(j/s) |
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Efficiency |
Calculating efficiency of energy transformation output/input •100 |
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