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Work and Energy

Discover the interplay of potential and kinetic energy through examples and the Work-Energy Theorem. Learn about gravitational potential energy and kinetic energy while exploring real-world scenarios like lifting, driving, and boiling. Sample problems included.

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Work and Energy

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  1. Work and Energy

  2. Work and Energy • Energy can be given to, or taken from an object by doing work. To understand this better, let’s brainstorm some types of energy…

  3. Types of Energy • Brainstorm!

  4. Potential Energy (Gravitational) • An object has energy because of how high it is. • ‘Stored energy’

  5. Kinetic Energy • An object has energy because it is moving.

  6. Pendulum • Energy is constantly changing from potential to kinetic to potential…

  7. Ok, let’s try some examples: • 1. A student lifting a box of books • 2. An athlete releasing a curling rock, which then slides on the ice to a stop. • 3. Robin Hood firing an arrow into a target. • 4. A car driving. • 5. Turning on a stove and boiling a pot of water.

  8. All the Energy!!! • When you really think about all the energy moving from place to place in every second of your day, it’s mind boggling!! Positive and negative work is constantly being done!! • * Remember that since work is a scalar, positive and negative work simply means that work is being gained or lost, it does not have a direction.

  9. Videos • The story of kinetic and potential energy • Potential energy: Wile E Coyote & Roadrunner • GED Physics: Kinetic and potential energy in a roller coaster

  10. Work-Energy Theorem • Energy is usually defined as the ability to do work. A moving object can do work on another object it strikes. A moving object can do work on another object it strikes. A flying cannonball does work on a brick wall it knocks down or a hammer does work on a nail it strikes.

  11. Work-Energy Theorem • That is, a moving object exerts a force on a second object and moves it through a distance. An object in motion has the ability to do work and thus can be said to have energy.

  12. Kinetic Energy • Kinetic energy can be defined as:

  13. Some really neat algebra… • Therefore, the net work done on an object is equal to its change in KE:

  14. Sample Problems • 1. A 145 g baseball is thrown with a speed of 25 m/s. • A) What is its KE? • B) How much work was done to reach this speed starting from rest? 2. How much work is required to accelerate a 1000 kg car from 20 m/s to 30 m/s?

  15. Gravitational Potential Energy

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