Learning Goal: Demonstrate an understanding of simple machines.
Last period, we looked at the wedge, and at the lever.
With a wedge, we learned that when we apply force to one end, the wedge changes the direction of the force, sending it outwards to either side.
We also learned that a lever allows us to lift more weight when the fulcrum moves loser to the load.
Learning Goal: Student will demonstrate an understanding of Simple Machines.
Today, we will look at Inclined Planes.
. Mocomi video about Inclined Planes.
. Eureka! video about Inclined Planes
. And (what a surprise!) I found a song about Inclined Planes.
Watch this video about how to do the Inclined Plane activity.
Notice two things:
- the longer the inclined plane, the less force Pic needs to apply to push the stone up it
- When Harry pushed the inclined plane uder the stone, the direction of the force changes
Let's think about some applications of Inclined Planes.
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Go to the Simple Machines Part 2 assignment in your Google Drive, in 'Shared with you',
and
answer questions 1 and 2. Come back to the front.
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. If you twist an inclined plane....... you get a screw!
Let's think about some applications of screws.
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Go to the Simple Machines Part 2 assignment in your Google Drive,
and
answer questions 3 and 4. Come back to the front.
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. Let's look at Pulleys.
Watch this video about how to do the Pulley activity.
Did you see that you always have to pull a much longer cord to get a lower application of force?
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Go to the Simple Machines Part 2 assignment in your Google Drive,
and
answer question 5. Come back to the front.
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Mocomi video about wheel and axle
Eureka! video about Wheel and axle
Here is a non-video explanation of why
a wheel and axle makes work easier to do.
And.... wheels and axles form another simple machine - the gear.
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Go to the Simple Machines Part 2 assignment in your Google Drive,
and
answer question 6. Come back to the front.
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Let us summarize how simple machines work - watch this summary .....(If it's blocked, try this one)................................................................ o
The lower force that we can apply, when using a simple machine, is because of the mechanical advantage.
Now - look back at Mechanical Advantage. Remember the Eureka video about the two professors lifting a book.
They calculated the Mechanical Advantage as the force needed to lift the book right up divided by the force used
to lift the book with a simple machine.
Another way to describe Mechanical Advantage is : how much a machine multiplies the effort force put into it.
or, if we prefer to speak Math:
MA = (the distance over which one must apply the force)/(the distance one wishes to move an object)
or, simply
Load / Effort
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Go to the Simple Machines Part 2 assignment in your Google Drive,
and
answer question 7. Come back to the front.
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We will take a brief look at compound machines.
A compound machine is made up of two or more simple machines.
Let's look at a pair of scissors.
Here is an apple peeler.
Here are more examples of compound machines. With a neighbor, work together to try to identify
all the simple machines that make up the compound machine.
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Go to the Simple Machines Part 2 assignment in your Google Drive,
and
answer questions 8-11.
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