Work and Machines (PowerPoint download)

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					Work and Machines
Work equals Force times
A. Energy
B. Velocity
                          100%




C. Distance
D. Mass

                0%   0%          0%

                A.   B.    C.     D.
Work is measured in
A. Meters
B. Pounds              100%



C. Joules
D. Newtons

             0%   0%          0%

             A.   B.    C.     D.
          Work and
          Machines
1.   Describe what a machine is and
     how it makes work easier to do.
2.   Relate the work input to a machine
     to the work output of the machine.
     Which of these is an example of work
     being done on an object?
A.    Holding a heavy piece of
      wood at a construction site.
B.    Trying to push a car that
      doesn’t move out of deep
                                               86%


      snow.
C.    Pushing a child on a swing.
D.    Holding a door shut on a
      windy day so it doesn’t blow        9%
                                                     5%
                                     0%
      open.                          A.   B.    C.    D.
Machines Do Work
    A Machine is a device that changes
     force.
    Machines make work easier to do
     in three ways.
1.   Change the size of a force needed.
2.   Direction of a force
3.   Distance over which a force acts.
 What do machines do?
A.   Change the amount of
     force you exert or the    55%
     distance over which you
     exert the force.
B.   Increase the amount of                30%

     work that is done.
                                     15%
C.   Decrease the amount of
     work that is done.                          0%

D.   Eliminate friction.       A.    B.     C.    D.
Increasing Force
 Theupward force exerted by the
 jack is greater than the downward
 force you exert of the handle.
Increasing Distance
 Theywill do the same amount of work.
 Doing the work over a longer distance
 allows them to use less force.
 Changing Direction
 When  you use an
 ax to split wood,
 you exert a
 downward force as
 you swing the ax
 then it changes
 into a horizontal
 force that splits
 the wood apart.
How can a hockey stick be
considered a machine?
A.   It multiplies force.
B.   It multiplies          45%

     distance.                          36%


C.   It changes
     direction.                   18%



D.   It reduces friction.                     0%

                            A.    B.     C.    D.
 Pulling down on a rope to hoist a
 sail on a sailboat is an example of
 a machine.
A.   Multiplying the force you
     exert.                                  55%


B.   Multiplying the distance
     over which a force is
     exerted.                    25%


C.   Changing the direction in         10%         10%
     which a force is exerted.
D.   Reducing friction.          A.    B.     C.    D.
Input Force
The   force that you apply to
 the machine.
It is also known as the Effort
 Force.
Output Force
The   force that is applied by
 the machine.
It is also known as the
 Resistance Force.
A term that means the same thing
as output force is
A.   Input force
B.   Resistance force         90%


C.   Effort force
D.   Multiplying force
                                    10%
                         0%               0%

                         A.   B.     C.    D.

				
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