Mechanical Advantage You mean I don’t have to use the shovel?!
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Transcript of Mechanical Advantage You mean I don’t have to use the shovel?!
Last time we discussed the different simple machines:
Wheel & Axle
Think: Why do we use machines to doThink: Why do we use machines to do work instead of doing it ourselves?work instead of doing it ourselves?
Main Concept 5: Main Concept 5: What we really want to do is get theWhat we really want to do is get the
machine to work “efficiently”. “Efficient” machine to work “efficiently”. “Efficient” basically means to “work really well”.basically means to “work really well”.
Mechanical Advantage
• Ways of making WORK easier to accomplish (less effort):
OR
Both will get the same work done, but which one takes less effort
to accomplish the work?
Think: Does more power Think: Does more power alwaysalways mean less effort? mean less effort?
Think: In the Work & Power Lab, wereThink: In the Work & Power Lab, were the steps with more power easier the steps with more power easier
for you to do? (Less or More Effort?)for you to do? (Less or More Effort?)
Using a machine allows for moreUsing a machine allows for morepower with less effort from you!power with less effort from you!This is why we use machines.This is why we use machines.
Main Concept 6:Main Concept 6:Mechanical Advantage is all about Mechanical Advantage is all about
getting the machine to make the job as getting the machine to make the job as easy for you as possible!easy for you as possible!
The equation for M.A.
ForceInput
ForceOutput
The higher the Mechanical Advantage, the easier it is to move something.
Basic M.A.= 1 We want to make the MA number bigger!!!Means more Output from the machine, less Input force from you! = less effort!!!
The Big Point: We want machines to do The Big Point: We want machines to do as much work as possible with as little as much work as possible with as little
effort from us as we can!effort from us as we can!
Think about this: Computers continue toComputers continue toget easier and easier to use.get easier and easier to use.
Think about this: How have cell phones How have cell phones become easier to use compared to original become easier to use compared to original
phones or even early cell phones!phones or even early cell phones!
= MA
Mechanical Advantage
ForceInput
ForceOutput
Main Concept 7:Main Concept 7:
TheThe Higher thethe Mechanical Advantage,, thethe Easier it is to accomplish the work.it is to accomplish the work.
Fo
rce
Fo
rce
5 N5 N
5 N5 N= 1= 1
2 N2 N
8 N8 N= 4= 4
We want to make this number bigger = easier to do
Notice that when there is moreOutput than Input force, the
MA number increases!
What the machine doesWhat the machine does
What you do
Class Inquiry Activities
Mechanical Advantage
of Inclined Planes (Ramps) Lab
Mechanical Advantage
of Levers Lab
Fo
rce
M. A. of Levers ForceInput
ForceOutput
Work = Input Force x Input Distance Work = Output Force x Output Distance
Distance
Fo
rce
Distance
Don’t forget: Work of Input = Work of Output
In this case, with the fulcrum right in the center, the forces, distance and total input/output work are exactly the same!
Think: when force anddistance are exactly thesame; is there any M.A?
Think: If the Input and Output are exactly the same is there any point to using a machine?
So how can we increase M.A. of a lever?
Fo
rce
Fo
rce
DistanceDistance
We have to adjust how we set up the machine itself!
In this case we can move the fulcrum and change the distance of the output and input:
Notice that mathematically, even though the amounts of distance and force have changed the total work done on both sides remains the same!Notice what happens to
the force and distance ofeach side when we move
Fulcrum closer to the mass
Output: Less distance but more force! Input: More distance but less force!
Work = Output Force x Output Distance Work = Input Force x Input Distance
Class 1 Levers:
Notice that the effort Notice that the effort arms are different arms are different
lengths. lengths. Longer Input/effort Longer Input/effort
“arms “give the “arms “give the scissors more scissors more
mechanical mechanical advantage.advantage.
**In other words, it **In other words, it makes it easier to makes it easier to
cut stuff!cut stuff!
Output/Result Output/Result ArmArm
Input/Effort Input/Effort ArmArm
Output/Result Output/Result ArmArm Input/Effort Input/Effort
ArmArm
Class 2 Lever:
If we were to If we were to increase the length increase the length of the input arms on of the input arms on
the wheelbarrow, the wheelbarrow, we would give it we would give it
more mechanical more mechanical advantage.advantage.
In other words, it In other words, it makes it easier to lift makes it easier to lift
stuff. stuff.
Mass to be liftedMass to be lifted
M.A. of an Incline Plane:
To give this simple machine more mechanical advantage, simply make the ramp longer
Notice: Did the height of the ramp change?
The same amount of work was accomplished with less force on your part!
ForceInput
ForceOutput
The ramp is now longer and less steep
Distance
Work that needs to
be accomplished