# BIO 158- Chapter 4

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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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 Author: aab100687 ID: 80473 Filename: BIO 158- Chapter 4 Updated: 2011-04-18 23:23:25 Tags: Chapter Work Power Energy Folders: Description: Explaining the Causes of Motion without Newton Show Answers:

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