Some FItness Physics


As a card-carrying. seven-day-a-week gym
rat there is one thing of which I am certain. What propels me through the gym
are the smoothly coordinated actions of my glutes, my quadriceps, and my
hamstrings and that is how I have able to confidently saunter through the gym.
Of this I am unequivocally positive! You are right in the sense that the
mechanical energy is being generated is coming from your legs your muscles are
turning chemical energy of the carbs and the little fat and the sugars into
mechanical energy but the force the thing that’s changing your motion the
thing that’s propelling your feet forward is the frictional force between
your feet and the ground you do a lot of water aerobics right that’s true if
you’re in the water and you’re not touching the bottom and you try and walk
don’t go anywhere you did the Fred Flintstone thing but you don’t know
anywhere think about like trying to walk on ice very difficult and what’s
different about ice resistance is futile actually non-existent your muscles and
your foot are pushing on the ice but there’s nothing pushing back on you what
your muscles are doing is bringing the non plant foot forward how fast must my
non planted foot ahh a typical walking speed is something
like 3 miles an hour right so that’s a night of relatively comfortable brisk
walk right for somebody in reasonably good shape let’s call it a meter per
second you’re moving forward your hips your of your waist is moving forward at
a meter per second the foot that’s planted isn’t going anywhere that plant
foot spends half of its time at zero velocity
well foot that’s coming forward has to catch up pass you pass your hips and
then get in front of you it’s got to go forward at 2 meters per second just to
catch up there isn’t could look a whole upper part of my body is still moving like it’s just – Newton’s laws again right
your body’s moving forward if you suddenly stop your feet you’re gonna end
up doing a faceplant into something but the speed equation of that back leg
changes when you are running it does yeah
what’s the difference between walking and running is the question when you’re
walking one foot is always on the ground but when you’re running both feet spend
some time in simultaneous flight. So then that plant foot the foot that that you
are pushing off on she spends less than half of its time stationary so when you
are running that back leg does not have to move forward as fast relative all
your body your body right when you were walking these long-distance walkers they
do that thing they’re at the maximum overturn rate to keep a foot planted
their back leg when they pick that up it is moving forward very quick lawn
average throughout the motion twice as fast as the your body and these are the
things I think about well while I’m working out, right? I appreciate it, very
much and now our fellow gym rats get to think
about the physics of walking and running as well. Dr. Nichols Gross teaches physics at the esteemed Boston University see out there on the track brother. Thank you so
much, Aaron. yeah. Or in the gym. Yeah

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