Frequently asked questions from students
What is the brain made of?
The brain is a jelly like soft tissue suspended within the enclosure of the hard skull in a bath of cerebral spinal fluid. The brain is covered by three membrane layers in which the outer-most layer, called the dura-mater, is connected to the inside of the skull at various suture points which serve to suspend the brain within the skull. The brain sits atop the brain stem and the spinal cord extends from there. The spinal cord passes out through a hole in the base of the skull called the foramen magnum. The mass of the human brain is roughly 1.5 kg.
What is the mass of the human head?
The mass of the human head is somewhere between 4.5 kg to 5.0 kg which constitutes about 7 per cent to 8 percent of the whole mass of the human body. For example: to find the mass of your head = mass of your body (kg) x 0.08.
What happens if there is a severe impact to the head?
A blow to the travelling head can cause the head to rapidly decelerate (or quickly stop), while the brain continues in its movement, striking the interior of the skull. The inertia effects of the brain keeps it travelling forward to strike the inside surface of the skull.
The impact of the brain against the skull may cause bruising (contusions) and/or bleeding (haemorrhage) to the brain.
A severe blow to the head can cause the brain to bleed at the site closest to the point of impact. This is called a coup injury.
A severe blow to the head can cause the brain to be injured directly opposite the point of impact – on the other side of the brain. This is called a contrecoup injury.
Thus it is important to decelerate the head appropriately.
In all types of impacts, the head is subjected to a combined linear and angular (or rotational) acceleration.
Linear acceleration is considered to produce focal brain injuries while rotational acceleration produces both focal and diffuse brain injuries.
If an impact force is applied to the head, the head rotates about its point of articulation but not around its centre of gravity.
If a helmet is placed on the head then there is an increase in mass to the head and if there is an impact to the head then there will be an increase in the rotational acceleration effects of the head, therefore it is important to keep the increase in mass added to the head to a minimum.
The technology liner reduces the overall mass of the helmet. As it is a lighter helmet it will reduce the effects of rotational acceleration of the head during impact.
What are the effects of rotational acceleration on a helmeted head? Download: Rotational acceleration of the head
What is the basic Physics behind cone-head?
For helmets, made of one density hard foam, similar to the foam in bicycle helmets, which are involved in an impact, the head will experience a rapid deceleration. In other words there is a high deceleration of the head and the impact time of interaction is short. Hence the forces are readily translated across the thickness of the foam liner to the skull.
(HARD FOAM IN CONTACT WITH HEAD MEANS RAPID DECELERATION –> SHORT IMPACT TIME –> MAJORITY OF FORCE TRANSLATED TO SKULL –> HENCE HARD FOAM IS NOT VERY EFFECTIVE IN ABSORBING IMPACT FORCE)
For helmets with the technology liner (i.e. low density cones embedded within the thickness of the higher density foam) and are involved in an impact, the head will experience a gradual deceleration because of the crushing/compression of the cones. The cones reduce the deceleration of the head and the impact time of interaction is longer or the head stopping time is longer. Hence there is a reduction in the forces translated across the thickness of the new shock absorbing liner to the skull.
This is based on the impulse physics equation: Ft = m∆v where F = force;
t = time of impact interaction; m = mass of helmet; ∆v = change in velocity.
The technology liner is doing work in absorbing an impact force.
(SOFTER FOAM IN CONTACT WITH HEAD MEANS GRADUAL DECELERATION –> LONGER IMPACT TIME –> LESS FORCE TRANSLATED TO SKULL –> HENCE technology LINER ABSORBS MAJORITY OF IMPACT FORCE)
How do you solve the following physics problem relating to a typical biking accident?
For Question and Answer (Senior High School Level): Download: A 70 kg mountain bike rider problem
What material is the technology liner made of?
The material that the technology is presently made of is expanded polystyrene foam (EPS). For further information on foams used in bicycle helmets click on the following link from the Bicycle Helmet Safety Institute: http://www.helmets.org/foam.htm#cone-head
Why incorporate cones within the thickness of the foam liner?
Cones have the unique property that when a force is applied to the cones they’ll readily compress, and as the force is continued to be applied, the cones will continue to compress but they’ll become harder to compress.
Also, cones are great shock absorbers.
So if we incorporate the layer of cones in a thickness of different density foam, like we have in the conehead technology helmets, and apply an impact force to the liner, the tops of the cones will compress. The collapsing of the cones causes the inpact energy to spread sideways within the thickness of the foam liner instead of towards the head.
What are the Standards for testing helmets?
For information on the different World standards for testing helmets click on the following link from the Bicycle Helmet Safety Institute: http://www.helmets.org/index.htm#standards
Other Resources for students:
Is a Helmet Worth It?
How Brain Injuries Affect Different Body Functions: http://www.dandalaw.com/resources/is-a-helmet-worth-it/
(Recommended by two students: Elizabeth and Patricia under Supervision of Teacher Rachel Martin; Albany, NY, USA)
Should a helmet be used for head protection while riding a bicycle?
Dangerous Decision – The Consideration for Helmet Use at Any Speed by J. Raleigh Burt (Published March 2005): Download
“My test results and research convincingly suggest that the velocity and energy created in a simple tip-over fall, onto a hard surface, are more than great enough to cause a serious head and/or brain injury to a cyclist not wearing a helmet, regardless of ground speed.”
~ J. Raleigh Burt (Author of ‘Dangerous Decision’)