Wednesday, November 13, 2013

Physics News in Real Life: Would your helmet crack if you fell off of a horse while jumping? Would your neck break?

Physics News in Real Life: Would your helmet crack if you fell off of a horse while jumping? Would your neck break? How was it that the Irish jockey, Peter Toole became paralyzed from the neck down after his “Fall From Grace” during a jump on Fine Parchment at Aintree Racecourse?
By Analiza Grabowski

-Jockeys take a serious risk when they race, risking serious injury. When they fall, if they fall in any wrong way, the jockeys can be seriously injured and can suffer very serous injuries from paralysis to death.

Assumptions:
Rider wearing a Troxel helmet
The foam on the inside of the helmet is 1 inch thick= 0.0254m
Weight of horse: ½ ton = 454 kg
Height of horse: 10 ft = 3.048 m
Height of fence: 6ft = 1.8 m
Average jockey weight= 50 kg

What we know:
Troxel riding Helmets are designed to sustain impact from a 9-10 foot fall off of the horse and it would take a force of would take 200G’s to crack the helmet with an assumed direct impact

Some Facts:
What helmets do: “Cycle helmets protect the head by reducing the rate at which the skull and brain are accelerated or decelerated by an impact. The helmet acts like a shock absorber. As it is impacted, the expanded polystyrene liner is intended to crush, dissipating the energy over a rapidly increasing area like a cone.” < http://www.cyclehelmets.org/1139.html>

Calculations:
Δ E = Fr

KE = 1/2mv2 = ½ (50kg)(14 m/s)2 = 49000 J

PE = mg(Δh) = (50kg)(-9.8m/s2)(-4.848m) = 2375.5 J

Etotal = 51375.5 J

The rider hits the ground and rolls (v from KE)
*Assume that the rider continues in the x direction (rolling)
*Assume PE is converted to Force, because still going in x direction (full KE present) goes from ΔKE = 0 because there is no change in velocity during collision to full KE when moving in the x direction then PE = 0

ΔE = mgh = ΔPE = -2375.5 J (negative PE)
^^^From the top of horse (above the jump) to collision (hitting the ground)

w = Fdcosθ
F = force, w = work, d = thickness of the foam, cos θ = 1

w = ΔKE = -2375.5 J = F(0.0254m)(1)
F = -93524.4 N convert to g’s to see if the helmet is cracked!
93524.4 N (1g/9.8 N) = 9543.3 g’s

Therefore the Helmet cracks (five times over!)!!!

Pressure = F/A
Lbs = F/A
Looked up pressure = 1000lbs/ Area of neck
Convert lbs to Newtons (looked up)
F = 4448.2 N to snap neck
Convert to g’s = 445g’s; so yes the neck is snapped.

Summary:
This was done with the assumption that the jockey fell off the horse and onto his head directly. In real life, you’re not going to land on your head every time; and there is no guarantee that you are going to break you neck. But, it is very difficult to solve for a person rolling, as there are so many factors involved, including your body absorbing energy, friction, using muscles as springs and controlling their fall. However, it can be assumed that a fall at this average speed and from the height of a jump such as this from a tall horse, you will be very hurt. This is why it makes sense why this rider (Peter Toole) is now paralyzed after his fall. Though, he probably didn’t land on his head, he clearly did not land well and was very seriously hurt. He was in a coma for three days after the fall, and suffered brain bleeds. An image of this fall is below:

<http://www.mirror.co.uk/sport/horse-racing/aintree-carnage-jockey-peter-toole-121815>