BIO 158- Chapter 4

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aab100687
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80473
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BIO 158- Chapter 4
Updated:
2011-04-18 19:23:25
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Chapter Work Power Energy
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Explaining the Causes of Motion without Newton
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  1. What is work?
    • It is the means by which energy is transferred from one object or system to another.
    • U = F(delta d)
    • The unit of measurement is the Joule, J
  2. What is energy?
    • In mechanics, energy is defined as the ability to do work.
    • Energy comes in many forms: heat, light, sound, chemical, mechanical
  3. Kinetic Energy
    • Energy due to motion
    • A moving object has the ability to do work because of its motion.
    • The unit of measurement is the Joule, J
    • KE =1/2mv2
  4. Potential Energy
    • Energy due to motion
    • Two types: Gravitational and Strain Energy
  5. Gravitational Potential Energy (GPE)
    • Potential energy due to an object's position relative to the earth.
    • GPE of an object is related to its mass(m) and the height of the object (h)
    • Unit of measurement is the Joule, J
    • GPE = -mgh
  6. Strain Potential Energy
    • Due to the deformation of an object.
    • SPE of an object is related to its material properties (k) and the amount of deformation (x)
    • The unit of measurement is the Joule, J
    • SPE = 1/2kx2
  7. Work-Energy Relationship
    • The unit of measure for work and energy is Joules.
    • Work is the means by which energy is transferred from one object to another object.
  8. Demonstrating the Work-Energy Relationship
    The work done equals the change in gravitational potential energy.
  9. Work-Energy Principle
    • The work done by external forces (other than weight) acting on an object causes a change in energy of the object.
    • U = delta E
    • U = deltaKE + deltaGPE +deltaSPE
  10. Conservation of Mechanical Energy
    When is Mechanical Energy Conserved?
    • When no external forces, other than weight, act on the body.
    • If there are no external forces, other than weight, acting on the body, NO WORK is done.
    • If no work is done, the total mechanical energy of the object is conserved (i.e., it cannot be changed; it remains constant)
  11. Conservation of Mechanical Energy (2) continued...
    • Thus, it can be used to analyze situations in which no work is done.
    • For instance, in the pole fault, the vaulter does no work during the vault itself (i.e., once he or she leaves the ground)
    • (KE + GPE + SPE) initial = (KE + GPE + SPE) final
  12. Power
    • The rate of doing work or how much work is done in a specific amount of time.
    • It can also be thought of as how quickly or slowly work is done.
    • The unit of measurement is the Watt, W
    • Power can also be defined as... average force times average velocity (Fv) along the line of action of that force.

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