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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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 views: 3 posted: 2/3/2012 language: pages: 15