Mechanical Advantage
You mean I don’t have to use the shovel?!
Main Concept 5:
Think:
Why
do we
machines
Last
time
we use
discussed
the to do
What
we
really
want
to
do
is
get
the
different
machines:
work
insteadsimple
of doing
it ourselves?
machine to work “efficiently”. “Efficient”
basically means to “work really well”.
Wheel
& Axle
Mechanical Advantage
• Ways of making WORK easier to
accomplish (less effort):
OR
Main Concept 6:
Both
will
getWork
the same
work
done,
Mechanical
Advantage
is
all
about
Using
a the
machine
allows
for
more
Think:
In
&
Power
Lab,
were
Think:
Does
more
power
getting
the
machine
to make
the
job as
but
which
one
takes
less
effort
the steps
with
more
power
easier
power
with
less
effort
from
you!
for
you
as
possible!
always
mean
less
effort?
forThis
you
to
do?
(Less
or
More
Effort?)
toeasy
accomplish
the
work?
is why we use machines.
The Big Point: We want machines to do
as The
much work
as possible
with
as little
equation
for
M.A.
effort from us as we can!
Output Force
= MA
Input Force
Think
aboutthe
this:
Computers Advantage,
continue to
The
higher
Mechanical
get easier
easier something.
to use.
the easier
it isand
to move
Think about this: How have cell phones
We want to make the MA number bigger!!!
Basic
M.A.=
1
become easier
to use
tomachine,
original
Means
more compared
Output from the
lesseven
Input force
= less effort!!!
phones or
earlyfrom
cellyou!
phones!
Mechanical Advantage
What you do
5N
8
=4
1
5
2N
Notice that when there is more
Output than Input force, the
MA number increases!
Force
Output Force
Input Force
Force
We want to make this number
What the machine does
bigger = easier to do
Main Concept 7:
The Higher the Mechanical Advantage,
the Easier it is to accomplish the work.
Class Inquiry Activities
Mechanical
Advantage
of Levers Lab
Mechanical
Advantage
of Inclined Planes
(Ramps) Lab
Output Force
Input Force
M. A. of Levers
Think: If the Input and Output are exactly
the same is there any point to using a machine?
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!
Distance
Work = Input Force x Input Distance
Force
Force
Think: when force and
distance are exactly the
same; is there any M.A?
Distance
Work = Output Force x Output Distance
So how can we increase
M.A. of a lever?
We have to adjust how we set up the machine itself!
Notice that mathematically, even though the amounts of distance and force
Notice what
happens to
have
changed
the
total
work
done
on
both
sides
remains
the
same!
In this case we can move the fulcrum and change
the force and distance of
the
distance
of the
and input:
Output:
Less
distance
butoutput
more force!
Input: More distance
but
less we
force!
each side
when
move
Fulcrum closer to the mass
Force
Force
Distance
Distance
Work = Output Force x Output Distance Work = Input Force x Input Distance
Class 1 Levers:
Output/Result
Arm
Output/Result
Arm
Input/Effort
Arm
Notice that the effort
arms are different
lengths.
Longer Input/effort
“arms “give the
scissors more
mechanical
advantage.
**In other words, it
makes it easier to
cut stuff!
Input/Effort
Arm
Class 2 Lever:
Mass to be lifted
If we were to
increase the length
of the input arms on
the wheelbarrow, we
would give it more
mechanical
advantage.
In other words, it
makes it easier to lift
stuff.
Class 3
Levers:
M.A. of an Incline Plane:
Output Force
Input Force
The same amount of work was accomplished with less force on your part!
Work that needs to
be accomplished
The ramp is now
longer and less steep
To give this simple machine more mechanical
advantage, simply make the ramp longer
Notice: Did the height of the ramp change?