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Physics

Physics. Energy. It is a quality that a body has after work has been done on this body. Kinetic Energy, the energy in motion. Potential Energy, the energy at rest. Energy. Sample problems:

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Physics

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  1. Physics

  2. Energy It is a quality that a body has after work has been done on this body. Kinetic Energy, the energy in motion. Potential Energy, the energy at rest.

  3. Energy Sample problems: 1. A body of a mass 4 slugs is held by an agent at a distance of 6 f above the surface of the earth. The agent drops the body. What is the speed of the body when it is on the way down at a distance of 2 feet above the earth’s surface?

  4. Energy Solution:

  5. Power It is the rate of doing work.

  6. Power Sample Problem: An airplane engine weighing 4,000 lbs is hoisted at a vertical distance of 9 feet to install it in an aircraft. The time taken for this piece of work was 5 min. What power was necessary?

  7. Power Solution:

  8. Alternate Form of Power There is another way of writing the formula that is, . Since , then . This is useful obtaining the an expression for the power output of a turbine engine. Which, these engines are rated in terms of thrust they produce and their power output is expressed by multiplying their thrust to the speed of the plane (units, HP)

  9. Alternate Form of Power Thus, or

  10. Exercises • A body of mass 10 kg, falls to the earth from height of 300 m above the surface of the earth. What is the speed of this body just before it touches the ground? • An elevator cab weighs 6000 N. it is lifted by a 5kW motor. What time is needed for the cab to ascend a distance of 40 m?

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