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# 02-06-08 - Energy-Kinetic Energy

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### 02-06-08 - Energy-Kinetic Energy

1. 1. Unit 8 (Chapter 10 & 11) Work, Energy and Power
2. 2. Work <ul><li>“ Work” means many things in different situations. </li></ul><ul><li>When we talk about work in physics we are talking about applying a force over a certain distance. </li></ul><ul><li>For work to occur a force must produce motion in the direction of the force. </li></ul><ul><li>Work = Force x Distance </li></ul>
3. 3. Power <ul><li>How fast work gets done is called power </li></ul><ul><li>Power is measured in a unit called watts </li></ul><ul><li>A powerful machine can do the same amount of work in less time than a less powerful machine </li></ul><ul><li>1 watt = 1 joule/sec </li></ul><ul><li>Horsepower is the English unit for power. </li></ul><ul><li>1 horsepower = 746 watts </li></ul><ul><li>Power = work </li></ul><ul><li>time </li></ul>
4. 4. Energy <ul><li>Energy is defined as the ability to do work </li></ul><ul><ul><li>6 Types of energy </li></ul></ul><ul><ul><ul><li>Kinetic Energy: associated with motion </li></ul></ul></ul><ul><ul><ul><li>Heat: associated with the speed of internal particles </li></ul></ul></ul><ul><ul><ul><li>Chemical: bonds atoms together </li></ul></ul></ul><ul><ul><ul><li>Electromagnetic: moving electric charges </li></ul></ul></ul><ul><ul><ul><li>Nuclear: in the atomic nucleus </li></ul></ul></ul><ul><ul><ul><li>Potential Energy: energy of position (energy at rest) </li></ul></ul></ul>
5. 5. Energy <ul><li>The units of energy are joules </li></ul><ul><li>joules are also the same unit as work! </li></ul><ul><li>(How Confusing!) </li></ul><ul><li>You can think of energy as stored work – that is ready to be released! </li></ul><ul><li>Energy cannot be created or destroyed – only changed from one type of energy to another! </li></ul>
6. 6. Kinetic Energy <ul><li>Energy with motion </li></ul><ul><li>Energy an object has because it’s in motion </li></ul><ul><li>All moving objects that have mass have kinetic energy </li></ul><ul><li>As mass increases, the KE increases </li></ul><ul><li>As speed increases, the KE increases </li></ul><ul><li>KE changes more with speed than with mass </li></ul><ul><li>KE = mass x speed 2 </li></ul><ul><li> 2 </li></ul>Kinetic Energy Kinetic energy (joules) KE = ½ m v 2 m - mass of the object in kg v - speed of the object in m/s KE - the kinetic energy in J
7. 7. Kinetic Energy depends on two things: mass and speed The amount of kinetic energy the cart has is equal to the amount of work you do to get the cart moving A cart at rest has NO Kinetic energy Applying a force can give the cart speed, and therefore kinetic energy. Applying a greater force increases the speed and therefore the kinetic energy Increasing the mass also increases kinetic energy because it takes even more force to push.
8. 8. Work-Energy Theorem the net work done on an object is equal to its change in kinetic energy
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