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Transformation of Potential and Kinetic Energy Work by rt3463df

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									                            Work
 PS-6.3 Explain work in terms of the relationship among the force
applied to an object, the displacement of the object, and the energy
                       transferred to the object.

 PS-6.4 Use the formula W = Fd to solve problems related to work
                       done on an object.
                    Work
• The product of:
  – the force applied to an object and
  – the displacement the object is moved, in the
   direction of the force


• Work, force, and displacement are
  quantities that have magnitude and
  direction
What do
  you
 think?
                    Work
• In order to do work on an object…
  – A force must be applied to the object
  – The object must move in the direction of the
    force (displacement)
           Work and Energy
• When work is done on an object, energy is
  transferred to that object.
  – Work is equal to the change in energy
  – When a net force is applied to an object and it
    moves, the work is transformed to kinetic
    energy
    • The kinetic energy will be greater if
       – A greater force is added
       – If it is applied over a greater distance
      Which takes more work?
• Suppose the ramp and staircase was the
  same height. Would it take more work to
  lift a ball to the top or to roll it up the ramp
  to the top?
                   Height
• If an object is lifted to some height, it gains
  gravitational potential energy equal to the
  work done against gravity to lift it to that
  height
  – The work done against gravity is the same
    whether the object was lifted straight up or
    rolled up a ramp
  – The greater the height, the more gravitational
    potential energy the object has
             Work Formula
• Work = Force * displacement
• W = Fd
  – Work is measured in Joules (J)
• F=W/d
  – Force is measured in Newton’s (N)
• d=W/F
  – Displacement is measured in meters (m)
    W

F       d
              Example 1
• A fork lift moves 34m carrying a 1023N
  box across the warehouse floor. How
  much work is done by the fork lift?

W = Fd
W = 1023 N * 34 m
W = 34,782 J
              Example 2
• How much work is done by a person who
  uses a force of 27.5N to move a grocery
  buggy 12.3m?

W = Fd
W = 27.5 N * 12.3 m
W = 338.25 J
              Example 3
• You and 3 friends apply a combined force
  of 489.5N to push a piano. The amount of
  work done is 1762.2J. What distance did
  the piano move?

d=W/F
d = 1762.2 J / 489.5 N
d = 3.6 m
              Example 4
• 55, 000J of work is done to move a rock
  25m. How much force was applied?

F=W/d
F = 55,000 J / 25 m
F = 2,200 N
                                Practice
1. Calculate the amount of work done when moving a 567N crate a distance of 20
   meters.

2. A fallen tree is lifted 2.75 meters using a force of 1565N. How much work is
   done?

3. If it took a bulldozer 567.6 joules of work to push a mound of dirt 30.5 meters,
    how much force did the bulldozer have to apply?

4. A frontend loader needed to apply 137 Newton's of force to lift a rock. A total of
   223 joules of work was done. How far was the rock lifted?

5. A young boy applied a force of 2,550 Newton's on his St. Bernard dog who is
   sitting on the boy's tennis shoes. He was unable to move the dog. How much
   work did he do trying to push the dog?

6. If it takes 68 joules of work to push a desk chair across a floor 12m, what force
    would be needed?

7. If a long distance runner with a weight of 596.82 newtons does 35,674.7 joules
    of work during a portion of a race, what distance will she cover during that
    portion?

								
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