20
Foundations of Engineering & Technology
Copyright Goodheart-Willcox Co., Inc.
Hammers are also used to remove nails. This
requires the exertion of heavy pressure. Using their
knowledge of mathematics and science, early engineers
looked to mechanical advantage to develop a way to
remove nails. Mechanical advantage is a measure of e
the ability to amplify the amount of effort exerted using
some type of mechanical device. Using mathematical
practices to calculate mechanical advantage, engineers
solved the problem by adding a claw to the back of
the hammer, Figure 2-3. The claw is used as a lever,
amplifying the ability to pry a nail out of the material
without exerting a great deal of effort. This process of
developing and improving technologies using knowl-
edge of mathematics and science is engineering.
OlegSam/Shutterstock.com
Figure 2-3. An example of mechanical advantage is using
the claw on a hammer to remove a nail.
STEM Connection:
Science and Mathematics
Calculating Mechanical Advantage
Tools and machines are developed to extend human capabilities by achieving
mechanical advantage. Recall that mechanical advantage is a measure of the
ability to amplify the effort exerted using some type of mechanical device. When
greater mechanical advantage is achieved, greater tasks can be accomplished.
Determining the best ways to achieve mechanical advantage when using machines
requires scientific knowledge of materials and forces and mathematical abilities to
understand and calculate the level of mechanical advantage achieved.
Tools and machines are classified as one or more of six simple machines. Simple
machines are the most basic mechanisms used to change a force being exerted to achieve
some type of task. The six simple machines are the lever, wheel and axle, inclined plane,
wedge, pulley, and screw. The claw found on a hammer or an adze is used to remove nails.
It is considered a lever because it provides leverage to remove nails. A lever is comprised of
a rigid bar that rests on a fulcrum, or a pivot point, to make moving objects easier.
Claws achieve mechanical advantage by converting
a small input force into a larger output force. Mechanical
advantage is calculated as a ratio of output force to
the input force. Therefore, if a claw produces an output
force 10 times greater than the force applied, it has a
mechanical advantage of 10. To calculate the estimated
mechanical advantage of a lever, use this formula:
mechanical advantage (MA) =
effort arm length
load arm length
The effort arm length is the distance between the
spot where effort is applied and the fulcrum. The load
arm length is the distance between the load that will be
moved and the fulcrum. See Figure A. The effort arm
length is 5″ and the load arm length is 1/2″, ″ providing a
mechanical advantage of 10. This means that the claw
multiplies the input force exerted 10 times.
Load
Effort
Fulcrum
Load arm
½ inch
Effort arm
5 inches
cagi/Shutterstock.com
Figure A. Calculating the mechanical advantage of
a lever.