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Physics/Treadmill vs terrestrial running


QUESTION: I read about  DARPA project to build low power jetpacks to assist soldiers to be able to run faster under load. Would a physical assistance like a powered back pack assist a runner on a tread mill as well? It seems not to me. The treadmill runner is not actually moving but is remaining stationary. It is the treadmill's belt that is moving. What do you think?

ANSWER: Actually, it would.  Not only could it provide a lifting force to make the runner not so heavy on their own legs, but most treadmills have an adjustable incline.  If the runner was running with zero incline, then it would just make it easier for them not to have to land on their legs.

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QUESTION: I guess I am just not getting it. The jet pack would provide forward thrust not lift in order to get soldiers running 4 minute miles with field packs. Somehow I do not see how forward thrust assists when moving your legs but keeping your body position stationary on a moving belt.


I haven't heard of this project before today, but it was easy enough to google it.  Perhaps seeing the video will help you visualize the forces.  See here:  The jets do point at a downward angle to reduce weight and provide thrust (the treadmill is on an upward slope), and there's even video of them testing it at the beginning on a treadmill.  The project is still under development.


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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