PULLEYS are Simple Machines, too

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(No Transcript)
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PULLEYS are Simple Machines, too!
YEAH!
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1 Joes Got Problems
actually just one BIG problem.
His problem is his pooch, Rex. Hes one sick
puppy. Hes also freakin HUGE!
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2 At the vets office
Joe has to get Rex up onto the examination table.
Yikes!
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3 Joes been working out
but not enough. Rex is just too heavy to lift.
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4 Joe learns his lessons well!
Yo, uncle! WhaddooIdo?
Use a PULLEY, Joe! Im busy, so I gotta go!
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5 But Joes new at Pulleys
so he does what anybody shoulda little research!
Pulley arrangement of wheel(s) and rope
that reduce the amount of force needed to raise
an object.
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6 He tries the first one
Fixed pulley uses one wheel to change only the
direction of force.
A fixed pulley wasnt broken and is now
repaired. Fixed in this sense refers to the
fact that the wheel is attached to the ceiling
and spins in place.
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7 Joe Pulls
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8 And
nearly breaks his back.
Oh yeah! Joe remembers seeing that a fixed
pulley just lets you pull down on rope instead of
pulling up on the object. It doesnt make Rex
feel one ounce lighter!
People do use fixed pulleys because pulling down
on rope is easier on the body than bending over
to pick the same weight up.
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9 Joe tries a different pulley
Movable Pulley uses a wheel hung on a rope to
pull upwards, reducing the force by half.
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10 Joe Pulls
and starts to lift Rex off the ground!
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11 But theres one issue
Joe cant get Rex high enough to get on the
table. On his tippy toes, Joes just not tall
enough to keep pulling up and up and up on the
rope. Rex only makes it halfway to the table
top. ?
Dang!
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12 Joe hatches a plan
He realizes that both the fixed pulley and
movable pulley have advantages and disadvantages
The fixed pulley doesnt make Rex feel any
lighter, but the movable pulley did allow Joe to
lift his sick pooch off the ground.
The problem with the movable pulley was having to
keep pulling up, up, up. However, the fixed
pulley does allow you to pull down on rope.
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13 Hmmm
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14 The Plan!
Combine the ADVANTAGES of the fixed and
movable pulleys without suffering the
DISADVANTAGES of either!
Eureka!
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15 Joes Research
Joe uncovers a way to string this all together so
that it helps him get the job done!
Double Pulley a combination of fixed movable
pulleys that reduces the force by half
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16 The Double Pulley at Work
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17 Joe Pulls
and starts to lift Rex off the ground!
And the good news is that he is able to pull down
on the rope so that he can just pull, pull, pull.
Rex goes up, up, up.
I rule!
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18 And Joe Has Just Accomplished

• Reducing the amount of force it took to do work.
• Making sure he got to pull in a direction thats
  easy for
• humans to do.
• Yes, he had to pull more rope, but thats a
  trade-off worth
• making.

This was possible due to mechanical advantage.
The movable and double pulleys make work feel
easier!
But most importantly
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ARF!
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20 And Thats
THE END!