Grade 8 Mechanical Systems
Topic 1: Mechanical Advantage
What is Mechanical Advantage?
Mechanical advantage is the comparison of the
force produced by a machine to the force
applied to the machine.
In other words, mechanical advantage is the
comparison of the size of the load to the size
of the effort force.
What is Mechanical Advantage?
The smaller the effort force compared to the
load, the greater the mechanical advantage.
What is Mechanical Advantage?
The formula for Mechanical Advantage is
MA = Load Force(LF)
Effort Force (EF)
= LF
EF
No units are used to express mechanical
advantage because it is a ratio. (The units
cancel out).
What is Mechanical Advantage?
If a branch lever has exerted a force 5 times
greater than the force you exerted on it, what
does that mean? The lever makes the job 5
times easier. (It takes only 1/5 of the unaided
effort to lift the car.)
What is Mechanical Advantage?
Machines can have a mechanical advantage that
is greater than 1 or less than 1 or equal to 1.
MA > 1
MA < 1
What is Mechanical Advantage?
Some machines do not have any effect on the
effort force that you exert. They simply change
the direction of the effort force.
100 N
MA = 1
MA = 1
Another Way to Calculate MA
The concepts of mechanical advantage and work can be
linked.
The closer you are to the fulcrum, the harder it is to lift
an object. The longer the effort arm, the less effort it
will take to lift an object.
MA = 1
MA = 5
MA = 1/5
Another Way to Calculate MA
Another formula that can be used to calculate the
mechanical advantage of lever is:
MA = Effort Arm (EA)
Load Arm (LA)
= Load Force (FL)
Effort Force (FE)
Another Way to Calculate MA
An application of levers is “keyhole surgery” wherein a
long tube is pushed through the incision to the part of
the patient’s body requiring surgery. Electronically
controlled levers cut and sew as needed while the
surgeon watches on a TV screen.
Laparoscopic surgery
Another Way to Calculate MA
An example where you might want to increase the force
that you yourself exert would be using tweezers for
delicate precision work.
Tweezers can be used to pick up small,
delicate items that can be broken or
damaged if too much force is applied.
Speedy Levers
The advantage of a class 3 lever is that the force
will move the load a greater distance and at a
faster speed.
Speed is the rate of motion (how fast something
moves) or the rate at which something changes
position. It is defined as distance over time.
Speed = distance
time
Speedy Levers
Most of the levers inside your body have a
mechanical advantage smaller than one.
Because of these levers, humans are
capable of precision work as well as
speed and quick reflexes.
Machines Made to Measure
Some of the factors taken
into account when designing
products for people are fit,
comfort, function, design
(shape), ease, cost.
Ergonomics is science of
designing machines.
Machines Made to Measure
Ergonomics is
especially important in
the design of work
environments where
occupational safety is
an issue.
Machines Made to Measure
Carpal Tunnel
Syndrome is a common
problem for people who
type a lot. It causes
numbness and pain in
the joints.
Machines Made to Measure
A person can prevent or treat Carpal Tunnel
Syndrome by using other machines that put less
stress on fingers.
Review
The two formulas for mechanical advantage are
MA = Effort Arm (EA) or Load Force (LF)
Load Arm (LA)
Effort Force (EF)
Review
A person may choose to use a machine with a
mechanical advantage of 1 because it can
change the direction of the effort (e.g. a class 1
lever).