The physics of "back and to the left"

[Steve Barber]

The shot through JFK has already occurred before z228.
That's why his fists are already up near his throat.
IMO, the movement forward is part of his reaction to a shot that has already passed through him.
The main reason for thinking this is that JBC is already reacting violently by this point.

  Hi Dan,   Over the years, many people have made the mistake of saying that JFK "clutched his throat", or that his hands went for his throat. 
If you look closely, JFK's right hand is cupped over his mouth when it reaches its highest point, and his left hand shows his index finger  extended and partially curled, while the remaining 3 fingers are curled.  His thumb cannot be seen.  The left hand rises up against the underside of his right hand.   It looks to me as is JFK sudden slightly rising up and then sudden motion back down is the result of gagging, after the bullet passed through his throat. Thus, his hand cupped over his mouth.  As he turns his head to his left, his right hand remains in position and is level at one point with his cheek until he brings it down once Mrs Kennedy takes hold of his left arm.   The truth is, is that his hands never went near his throat.

[Steve Barber]

Interesting.

Two shots at approximately z228. One from the front right, and one from the rear. Synced

fractionally first shot in the back. below



and the shot from the front right hitting the chin, in this instance.

  Oh, so now you've personally moved the exit wound in the throat up to the chin.  Aren't you one of those who are always citing the doctors at Parkland describing the wounds as accurate?   IF so, why didn't anyone mention a wound on the chin?  Where do you come up with such things?

 


And Bingo! same sequence of events at z228 are repeated in z313. A shot hitting JFK in the back and shot from the rear, simultaneously ... a kill shot from the front right.

 Really?   How did a shot from the front throw head matter all over the entire inside of the limousine, the windshield, the hood of the car, the side rails, the inside and outside of the right sun visor, Greer, Kellerman, and the Connally's?  And why do we see the top of JFK's head fly through the air, only to land in pieces several yards ahead of where the limousine was positioned at the time of the fatal shot, only to be discovered by three different people, i.e. David Burros, and Seymour Weitzman who found skull fragments the day of the assassination, and Billy Harper, who found a fragment on the day after?  All of this points to the fatal shot having come from behind the president, and above and the trajectory of the head matter following the trajectory of the bullet-save for the minute spray that Hargis and Martin drove through and landed on them--not to mention can clearly be seen in the Zapruder film drifting to the rear with the breeze.

[Brian Roselle]

Steve, I agree with you that the "clutching the throat" after the ~z222 strike is probably not the whole story (and may not even be the main part of the story).

Two things have bothered me around the grasping for the throat or choking move as a reaction explanation.

The first is that a major contraction of the deltoids to raise the elbows up so high, for me that seems to actually put the hands a little too high to readily come back down and access the throat/neck, the chin become a blocking agent and would seem to hinder a quick natural throat protection response. Having the elbows down low and with just flexing the forearms up to facilitate grabbing the throat seems more efficient natural emergency response there. That is one reason I don't like the throat grasping explanation.

The second is that I don't recall seeing any other really rigorous medical explanation for those reactions. They are so unusual, I would have expected to find more on what could cause it. I can't recall if I have linked this before, but I went looking in neurological resources and journals for possibly a more detailed explanation. Spastic Paralysis seemed to describe the injury caused by associated nerve trauma, and if the reactions can be quick to engage, JFK's condition on film looks to have most all the typical symptoms seen in the literature.

https://sites.google.com/view/spastic-paralysis/home
 
Sometime maybe I could find a top end neurologist to share this with and get comments on if this, vs. choking, is a more likely response to what we see on film.

[Gerry Down]

Could an alternative to the jet effect at Z313 be the piece of bone that shoots up at a 45 degree angle from the top of JFKs head? Would an opposite and equal reaction to this bone rocketing off from JFKs head cause JFKs head to be forced downwards, and with no where to go would cause JFKs head and body to subsequently spring "back and to the left".

Think about it. If you compress a spring, it will spring back and upwards away from where you applied the force downwards.

[Matt Grantham]

For one frame Most others in the limo are moving forward at that time

[Joe Elliott]

. . .

The second is that I don't recall seeing any other really rigorous medical explanation for those reactions. They are so unusual, I would have expected to find more on what could cause it. I can't recall if I have linked this before, but I went looking in neurological resources and journals for possibly a more detailed explanation. Spastic Paralysis seemed to describe the injury caused by associated nerve trauma, and if the reactions can be quick to engage, JFK's condition on film looks to have most all the typical symptoms seen in the literature.

. . .

JFK’s reaction to the neck wound is likely what is often called a ‘Thorburn reaction’, as theorized by Dr. John Lattimer. A doctor Thorburn described a similar response to a neck injury to a patient back in the nineteenth century. It seems that damage to a certain area of the spinal cord in the neck can trigger this response.

The two arguments that CTers used to dismiss this theory, are weak.

1.   Dr. Lattimer was a urologist.

This is true. But what is a urologist? A urologist is a medical doctor, who specializes in urology. But he is still a medical doctor who has received all the basic medical training, including the treatment of all sorts of wounds. That is why the U. S. Army drafted him in World War II to serve as a medical doctor with the Third Army in Europe. It wasn’t because they expected the largely youthful army to experience a lot of urinary problems. It was that he, a medical doctor, could treat battle wounds, like those caused by bullets. He was chosen for his expertise with wounds, which all medical doctors have.

In addition to his medical training, Dr. Lattimer gained a lot of real-world experience treating battle wounds, including rifle bullet wounds, during 1944-1945. More than any current doctor would likely receive. So, he was a strong candidate to evaluate JFKs wounds, which is why the Kennedy family selected him to look into it.

2.   The two cases, the nineteenth century injury and JFK’s injury have to have two separate causes, because the nineteenth century response took several days to take effect, while JFKs was almost instantly.

However, the nineteenth century damage to the spinal cord was caused by an infection, not a bullet. As I recall, a heavy weight struck the back of the neck of the victim. This did not cause any immediate damage to the spinal cord. But it did cause an infection to set in, which within a few days did reach the spinal cord and damage it, resulting in the victim raising his arms and holding them in a similar position of JFK’s. Except this patient was lying on his back in bed while JFK was sitting up.

Naturally, if in one case the damage is caused by a bacterial infection, the reaction could take a few days to set in. While in another case, if the damage is caused by a bullet, the reaction would be immediate.

Dr. John Lattimer stressed that this diagnosis is not based on his examination of the patient (naturally) but is based on the location of the bullet path near a certain section of the spinal cord and his study of the Zapruder film. Coming up with an accurate diagnosis is hard enough when one has a patient one can examine in person. It is even more challenging when it is instead based on looking at a film of the patient. Still, this is about as good a professional guess as we are ever likely to end up with.

[Brian Roselle]

As a disclaimer, I am not an expert in neurology and regarding the Thorburn position, I haven’t seen enough detail on its neurology to comment.
However when looking at the literature and causes/symptoms of spastic paralysis, Thorburn didn’t seem to come up in what I reviewed.

Having said that, I did see references where spastic paralysis could manifest itself rapidly as in a reflex, but also could develop over time (even weeks).

So, I am beginning to think Thorburn could be subset of Spastic Paralysis, and the original Thorburn case may refer to a slower onset version of Spastic Paralysis.

Here are a couple of references on Spastic Paralysis that describe onset times:

This reference mentions the occurrence of quick, reflex onset.

What is spasticity? (from https://msktc.org/sci/factsheets/Spasticity)
Spasticity is the uncontrolled tightening or contracting of the muscles that is common in individuals with spinal cord injuries. About 65%–78% of the SCI population have some amount of spasticity, and it is more common in cervical (neck) than thoracic (chest) and lumbar (lower back) injuries.
Symptoms and severity of spasticity vary from person to person and can include:
•   Sudden, involuntary flexing (bending) or extending (straightening) of a limb, or jerking of muscle groups such as in the trunk (chest, back, and abdomen), bladder, or rectum.
After a spinal cord injury, the normal flow of signals is disrupted, and the message does not reach the brain. Instead, the signals are sent back to the motor cells in the spinal cord and cause a reflex muscle spasm. This can result in a twitch, jerk or stiffening of the muscle.

This reference mentions a slower onset, even some with an initial flaccid paralysis. (from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2860542/)

More than 80% of people with Spinal Cord Injury (SCI) have spasticity, and many have greater disability from it. Spasticity develops gradually over several months after injury. Immediately following SCI, the spinal cord becomes areflexic (spinal shock), a period characterized by loss of tendon reflexes below the level of the lesion, muscle paralysis, and flaccid muscle tone.

Given what is seen in the Zapruder film, it does not look like a version of extended onset of spasticity with initial flaccid muscle tone, but rather the version with sudden stiffening of muscle tone.

This all could be semantical, as both terms refer to a neuromuscular response to spinal cord trauma, and it just boils down to what is the best name to associate with the reactions that were seen in that timeframe shortly after being struck. As spastic paralysis seems to be more encompassing regarding onset time, that is what I use.

[Andrew Mason]

Let’s take one point at a time.

JFK was sitting pretty much upright, with a slight lean forward. During the early part of the movement, z313-z316, the movement was even slightly “uphill”. But it never mattered. The acceleration was constant. Even when he did start to tilt backwards, the acceleration he would get from gravity was a fraction of the acceleration
Using physics graduate student Michael Hoffman’s calculations, the acceleration of the head during z314-z315. z315-z316 and z316-z317 was 0.26 G’s, 0.26 G’s and 0.17 G’s. Note, I converted Hoffman’s numbers from feet per second squared to G’s. If the head and body were reclined 90 degrees, lying flat on his back, and JFK was free to continue to fall, gravity could accelerate JFK’s head at 1.0 G’s.

1. First of all, you are assuming first that there is sufficient information in the zfilm for anyone to accurately determine the acceleration over the course of 5 frames. There isn't.

The zfilm is not continuous.  It represents a view taken for a 1/40th of a second (Zavada Report, Study 4, p. 16) or 25ms out of a total of 55 ms. between consecutive frames.

What we see up to the end of the exposure of z312 is no forward motion of the head or body.  What we see in z313 is that the head has moved forward a small but perceptible amount.  And we also see that the head has already exploded and there is a cloud of blood spray and some spray trails suspended in the air. So by the time z313 is exposed, the head has received a variety of forward and backward impulses separated in time as the bullet struck the head, then transited the head and then as the exit rupture forcefully caused an ejection of matter out of the head.

The net result of these impulses by the end of the exposure of z313 is a movement of the head slightly forward.  But a single exposure does not tell us how it is moving at that point. It could be moving backward, and in my view it must be (see point 5., below). To determine the acceleration between z313 and z314 (change in speed/time between 314 and 313) you need to know what its motion after exposure of z313 was. But that is a guess because that depends on the moment that the bullet struck the head and the zfilm does not tell us that. We also have a blur which makes it difficult to determine accurately the change in position of the head between those two frames.

Similarly, you cannot determine the acceleration between z314 and z315 (change in speed/time) unless you can determine its speed at the end of exposure of z314, which we cannot do.

So in order to analyse what is happening in z313 and after we need to know exactly when the bullet struck the back of JFK's skull.  The zfilm does not tell us that.

2. The head is not the only thing that you need to take into account. The head is connected to the upper body which is connected to the lower body which is sitting on a seat.  You need to examine the motion of the centre of mass but that is difficult because it is constantly changing.

3. The body is subject to gravity which also has to be taken into account. As the body is leaning forward initially, the rearward force on the head from the head explosion causes rearward momentum that causes the head and body to move back against gravity initially and then with gravity.

4. The neuromuscular mechanism is not clear. If the rearward motion of the body was the result of a neuromuscular response, it had to start within a frame of the bullet striking JFK's head and had to involve the contraction of muscles that would push on something in the car to drive the body rearward.  That means the legs would have to be involved and the only thing they could push on would be the seat and the floor.  But the legs are bent because he is sitting. It is difficult to understand how that could result in such sudden motion of the body. The force would have to be enormous to move the body that quickly.

5. In any event, the rearward momentum imparted by the head explosion cannot be ignored even if you think there is a remarkably fast neuromuscular response.   

The bullet was travelling at about 1900 fps or 580 m/sec when it struck the back of the head and the path through the head was about 8 inches or 20 cm.  We can see that the time for the passage of the bullet through the head is going to be on the order of a millisecond.

So for the transfer of bullet momentum to the head:

• forward bullet momentum = 6.1 kg m/sec  [(2000 fps = 610 m/sec) x .01 kg]
• mass of head 5 kg.
• assume all forward momentum transferred to head

So the speed of head from bullet impact but prior to head explosion: v=p/m=6.1/5 = 1.22 m/sec forward. That is the maximum possible speed as it assumes 100% of the bullet momentum is transferred to the head.

For the rearward momentum imparted to the head due to the head explosion:
Let's assume that the matter exploding from the head consisted of 1/4 to 1/2 of a kilogram and lets suppose that it carried 3/4 of the bullet energy (ie. .75 x 1860 Joules=1395 J.). 

The total momentum of the ejected matter is related to its energy (KE=1395 Joules): by KE=mv^2/2 = p^2/2m where p is the momentum, m is the mass of the ejected matter and KE is the kinetic energy. So p = (2mKE)^1/2 = (2 x (.25 to .5) x 1395)^1/2 =  26 to 37 kg m/sec. Since the explosion is in a semi-circle around the head, not all of this momentum is completely forward. Let's say a minimum of 50% and a maximum of 70% is net forward: 13 kg m/sec (if .25 kg ejected at 50% forward) to 26 kg m/sec (if .5 kg ejected at 70% forward)
So rearward impulse to the head would be, roughly, 13 to 26 kg m/sec.

This means the head (now about 4.5 to 4.75 kg) recoils with a minimum rearward speed of: 13/4.75 kg = 2.75 m/sec. up to 26/4.5= 5.75 m/sec.

So the initial rearward speed of the head is: 2.75 to 5.75 m/sec, much more than the maximum 1.22 m/sec forward speed from the bullet momentum. So it is moving backward at a minimum of 2.75-1.22= 1.5 m/sec. And it acquires that speed in the time it takes for the head explosion to occur. That has already happened by the time z313 was exposed so in z313 the head is already moving backward a minimum of 1.5 m/sec. due to the head explosion.  That would seem to me to account for all the motion seen after z313.