Design a Better Football Helmet Lesson
Lesson Description:
Recently, the NFL and other sports agencies have focused on the issue of
concussions. Players are often subjected to intense blows or collisions
on the field of play, and the number of concussions resulting from
inadequate head protection seems to be on the rise. This activity
allows students to use inquiry to investigate the materials used to make
sports helmets and to propose shell and cushioning material in
“designing a better football helmet.” The lesson allows students to
perform real scientific tests centered on a “real-world” problem. The
students, in the inquiry portion of the lesson, perform impact tests on
polymer samples by dropping a plumb bob from differing heights onto
the samples. The tests, modeled after actual industrial testing methods,
measures the toughness and brittleness of polymers that have been
subjected to intense blows. Both rigid polymer materials that may be
used in the outer shell of a helmet and foamed plastics that can be used
for the inner lining of the helmet are tested in the lab, and, upon lab
completion, students have to put forward their recommendation of a
combination of shell and lining material that might be used to create a
helmet capable of protecting players better than other combinations.
Objectives:
What should the students know as a result of this lesson?
Students will….
• know the importance of safety gear (helmets) used in sports.
• explain the purpose of an impact test.
• explain that impact resistance describes how a material reacts to
shock or sudden stress.
• identify the functions of the hard outer shell and the foamed inner
lining of a sports helmet.
• distinguish between the structure of a helmet made for multiple
collisions, such as a football helmet, and a helmet made for a
single collision, such as a bike helmet.
What should the students be able to do as a result of this lesson?
Students will….
• test the ability of various polymers to resist impact (sudden
blows).
• compute impact in inch-pounds or Newton-meters.
• work cooperatively.
• perform tests on materials designed to mimic actual industrial
tests and collect data.
• examine and analyze data collected from the testing of polymers
to determine which plastics would be most suitable for use in a
helmet.
Materials Needed:
Note: We obtained our impact testing kit (all materials required for
this lesson) from Educational Innovations, Inc. www.teachersource.com;
888-912-7474
 A video clip or picture showing a football tackle or a PowerPoint
or Keynote file with multimedia images and/or videos with lesson
description outlined step-by-step.
 Samples of a variety of hard plastics – cut nearly the same size each sample labeled with the correct name.
 Clear tube or stiff cardboard tube from a wrapping paper roll with
a viewing slit cut in the side. Tube should be at least 30 inches
long. Use a magic marker to mark off the tube at 6 inch intervals.
 Plumb bob or other standard weight to be used as a dropping
object.
 String - at least 36 inches long
 Piece of wood to set under the test area.
 Square block
 Safety goggles
 Ruler or meter stick
 Ring stand and clamp – optional
1 1/2” dia.
 PVC coupling or small diameter jar lid
 Lab Procedures (developed with students during discussion)
Lesson Plan (5-E model):
Engagement:
Show a short video clip, a series of clips, or a series of images using Keynote or PowerPoint of
football tackles and hits in the NFL and college games in order to catch students’ attention and
allow the presenter to present the lesson focus.
Interact with students to discuss the tremendous forces that athletes are asked to endure on the
field of play. Have students discuss minimum protective equipment, and have them focus on the
importance of having adequate protection in the helmet. The historical advancement of the
helmet from leather covering to its current incarnation might be prudent as well.
To make the initial discussion more interesting the following background information should be
discussed:
In sports, body armor is designed to protect the participant from projectiles (mainly
balls), from human impact, and from crashes. Many sports, such as football, cycling,
and baseball require athletes to wear helmets. The outer shell of the helmet must be
impact resistant while the interior must mitigate an impact by slowing the
deceleration of the head.
The National Operating Committee on Standards for Athletic Equipment (NOCSAE)
has developed voluntary test standards designed to reduce head injuries by
establishing requirement of impact attenuation for football helmets/face masks,
baseball/softball batting helmets, baseballs and softballs, and lacrosse helmets/face
masks. The various regulatory bodies for sports, including the NCAA and the
National Federation of State High School Associations have adopted these standards.
In football, on the field concussions are considered one of the most serious of
contact sports injuries. Concussions are most likely to happen as the result of a
blow to the side of the head, rather than the front or top, according to new research
conducted by Biokinetics & Associates. Football is responsible for approximately
100,000 concussions in the United States each year.
The NOCSAE test standard for football helmets involves mounting a helmet on a
synthetic head model and dropping it a total of 16 times onto a firm rubber pad
from a height of 60 inches. Drops are made onto 6 locations on the helmet. Most of
the drops are conducted at ambient temperatures, however, at least 2 of the drops
are conducted immediately after the exposure of the helmet to 120° F for four
hours. The equivalent of a 60-inch drop test would occur if a player running at 17.9
ft/sec (12.2 mph) ran into a flat surface which stopped his head in less than one
inch. Most players run faster than this (average speed of a player running 40 yards
in 4.8 seconds is 25 ft/sec) but vary rarely would the head be stopped in such a
short distance on the football field.
In baseball and softball, the primary hazard is being struck by a pitched or batted
ball. Therefore, baseball helmets are mounted on an instrumented headform that is
free to move. An air cannon is used to shoot a baseball from close range into the
helmeted headform at 60 mph. Impact accelerations are measured and a Severity
index is calculated.
Evaluation for Engagement Activity:
Assessment is informal at this stage. Try to involve all students in the
discussion. Allow students to cite examples from their own experiences relating to
the importance of protective sports equipment.
Exploration (Part One):
Allow students to test materials that could be used in the outer shell of a football
helmet.
Procedure:
Obtain the labeled plastic samples for testing. Set up the testing apparatus as shown.
The plastic sample can be placed on top of a PVC coupling or the rim of a jar lid so that
the weight can penetrate through the sample before hitting the wood. The end of the
tube should be immediately above the plastic sample.
Note: the tube can be held by hand if a ring stand is unavailable. Younger students may
want to hold the tube anyway – for a more secure grip.
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Unscrew the top of the bob and attach a string so that it is centered on the bob.
Lower the bob down through the tube so that it is 6 inches above the plastic
sample.
Release the string so that the bob falls freely onto the plastic sample. Inspect the
sample for cracks and breaks. Failure of a sample can be deformation that is
evident on the back side of the sample, crack initiation, or complete breakage.
If the sample has not "failed", increase the height from which the bob is dropped
by 6 inches. Keep increasing the drop test height by 6 inches each trial until the
sample is broken or until you have reached a maximum of 30 inches. Record the
height at which the sample breaks or the maximum height used to test it.
Multiply the height of the drop by the weight of the bob to obtain impact in inchpounds.
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Note: All Impact Standard testing is done in the English system in the Educational
Innovations Lab Activity but this can easily be converted to metric units. The unit of
measure for the impact test is the inch-pound. If a 10 pound weight is dropped an inch
onto the sample, then it equals 10 in-lb. Students will be using an 8 oz plumb bob (or 0.5
lb.). The plumb bob will be dropped through a tube from increasing heights onto the
plastic sample.
Assessment for Exploration (Part One):
Make sure students are following proper laboratory procedures. Monitor the
groups and make sure they are recording information on their worksheets. Collect
and evaluate student worksheets for completeness and accuracy.
Explanation for Exploration (Part One):
After completion of testing and recording of data, students should report their
findings and determine the most suitable outer shell material for use in a particular
type of helmet, of the ones tested, based on their results. There are no wrong
answers here as long as students can back up their statements using evidence from
their data.
Ask students to explain impact resistance and its importance in determining
materials to be used in the outer shell of a helmet. Make sure they know that impact
resistance describes how a material reacts to a shock or sudden stress. This test
measures the brittleness of a material that has been subjected to an intense
blow. The property of toughness describes the material's ability to withstand such
an impact.
To relate student testing to product development in industry let students know that
most product engineers do not use the results from impact tests alone to determine
which material will be used in a commercial product. Decisions may also involve
information gathered from tests such as stress/strain, tensile strength, ductility, or
thermal sensitivity. However, this lab concentrates on the impact resistance of
polymers that could be used in constructing sports equipment.
One test used in industry is the Gardner Impact Test. During this test, a
weight is dropped from a specified height onto a test sample until it
breaks. Although the sample may be any size, industry typically uses a 3 x
5-inch sample with a 1/16 to 1/4 inch thickness. (Since a teacher needs to
use whatever materials are readily available, sizes in this lab may vary. It is
suggested that samples should be as reasonably close in size as possible.)
Temperature is a major variable during testing. Most industrial tests are
conducted at 20° C. These tests will be conducted at room temperature.
The discussion in this section can now lead to the importance of the foam
linings placed inside of helmets. This leads you into Exploration 2.
Exploration (Part Two):
Allow students to investigate the properties of various polymer materials that could
be used to create the interior cushioning and lining of the football helmet. Testing
will be used to assess a material's ability to protect an object (such as a
head!). Weights will be dropped on various foam materials placed over a "fragile"
candy bar. Students will be able to determine which materials offer the best impact
attenuation and even be able to design their own materials for testing.
Procedure:
1. Using one type of foam material, set up the apparatus as shown below.
2. Hold the plumb bob, narrow end pointed downward at the top of the
tube. Drop the bob through the tube. Visually try to see how far the foam is
compressed. Measure the indentation.
3. Remove the foam material from the top of the candy bar. Check the bar for
breakage and cracks.
4. Repeat the drop test from the same height using the other available foam
materials.
Note: The candy bars can be frozen. If so, they will show even more damage resulting
from the drop. Allow students to suggest and try their own testing procedures if
reasonable.
Extension (Optional):
Allow students to design their own protective packing material. Mix various
combinations of ground up foam and rubber with a small amount of white glue. Two
sample recipes are provided.
1. Mix 1/4 cup foam with 1/4 cup rubber and 3 tsp of white glue. Press the
mixture into two cups of a muffin tin with a spoon. Allow the mixtures to dry
48 hours before testing.
2. Mix 3/8 cup foam with 1/8 cup rubber and 3 tsp of white glue. Press the
mixture into two cups of a muffin tin with a spoon. Allow the mixtures to dry
48 hours before testing.
3.
Students can also fill the muffin tin cups with foam sealants from spray cans such as
Dow's Great Stuff™ insulating foam sealant. Great Stuff™ can also be sprayed
directly onto wax paper.
Repeat the drop tests using the new packing materials and
compare results.
Assessment for Exploration (Part Two):
Make sure students are following proper laboratory procedures. Monitor the
groups and make sure they are recording information on their worksheets. Have
students report their findings. This can lead to a discussion on different types of
helmets and the use of rigid foam in some and soft foam in others. Again, any
student answer is acceptable as long as it can be supported by data.
Explanation for Exploration (Part Two):
Helmets work by bringing the head (and brain) to a relatively gradual stop upon
impact. When an unprotected head strikes against a hard surface, inertia causes the
brain to slam forward against the skull. This causes bruising and bleeding.
If you look inside most helmets you will see foam pads. The foam softens the shock
by gradually crushing to absorb impact energy, thus cushioning the blow. This slows
the stopping process from about 1 millisecond to 6 milliseconds, thus reducing the
spike of energy to the head and brain. As the foam crushes or deforms, it converts
some of the crash energy into heat.
According to the Law of Conservation of Energy, energy is not lost but converted to
some other form of energy. What a helmet does during a crash is referred to as
“energy management”. Some of the energy of the collision is converted to heat.
Current helmets perform energy management with some type of foam. There are
two types of foam: one type is stiff and crushable, the other is rubbery or
squishy. Their characteristics make it possible to design a helmet for one very hard
impact, a number of hard impacts, or a very large number of softer impacts. Denser
foams resist very hard impacts. Softer foams compress more easily in lesser
impacts giving better protection against milder injuries. Crushable foams are ideal
for helmets designed for one hard impact (like bike helmets). When the foam
crushes, it does not bounce back like a spring to make the impact worse. Rubbery
foams (football and skateboard helmets) provide multiple impact protection but are
less protective in very hard impacts.
Elaboration:
The instructor may choose to present information on the actual plastics used in
various helmet types or have students research this information on the Internet.
Students might try to hypothesize why one material is favored for football helmets
and others for baseball or biking helmets. Encourage students to suggest and try
their own testing methods on the plastics. Final Lesson Assessment:
Have students write a short report on their findings. This report can be collected
and evaluated or given orally to the class.
Sample Lesson Pictures:
Josh, my graduate fellow, is presenting the intial engagement portion of this lesson…
Josh, in the helmet, is helping students to perform the lab tests in the exploration
(Part One) activity…
Students are each performing the tests in the Exploration (Part One) activity…
The students in the last block decided to perform a high impact test by putting their
tubes together and testing materials again….inquiry learning usually leads to
additional activities (and learning) such as this.