(fig.1a) 1a) as well as petechiae in both ear canals and on the soft palate.Ī r = ( 20 k m h ) 2 1.2 m = ( 5.55 m s ) 2 1.2 m = 25.67 m / s 2. Additional findings of the physical examination included a mild swelling and periocular petechiae (fig. There was no limitation in ocular motility. Intraocular pressure was 12 mm Hg in both eyes, and pupillary responses were normal. The remainder of the examination was normal, with clear corneas and lenses, no intraocular hemorrhage of any kind and normal dilated fundus examination. Bilateral subconjunctival hemorrhages were noted in both eyes (fig. On examination, visual acuity was 20/20 OU. After dismounting the carousel, the boy complained of a headache, his face was swollen, both eyes were red and he was brought to the emergency room in our institution. The rapid spinning lasted for about 1 min, during which the boy suffered an intense headache, but did not lose consciousness. The boy had no control of the carousel, but fortunately an adult managed to disconnect the scooter. He had mounted a carousel that was attached to an electrical scooter, and had spun round on it very rapidly. Now when you are travelling in an elevator you only have an acceleration of 0.5g, so we can conclude that the elevator gives you a force of -0.5g in the upward direction, thereby reducing your weight.A healthy, 10-year-old boy was examined in our institution due to bilateral diffuse subconjunctival hemorrhage. But your body will have an acceleration of g if you were to jump of a building, given you measure it before you die -). Now coming back to your body, your has a downward acceleration of 0.5g. This is obvious since if you had a net acceleration you wouldn't be standing still inside the elevator. Now that means you in the elevator is also moving at 0.5g acceleration. So the net acceleration of the elevator now is g-0.5g=0.5g in the downward direction. Now the elevator according to your paragraph provides an upward acceleration of -0.5g. That is, the g-force(gravitational force) acts downwards, acceleration of g. When you are going downwards, what the elevator is doing is actually by a little counter acting the force of gravity. So we are going to take downward as positive and upwards as negative. Instead of the elevator floor accelerating you upwards the elevator roof accelerates you downwards.Īre you sure the paragraph is correct, because I can't make out which direction is positive. This is how your acceleration can become negative. ![]() If the acceleration of the elevator becomes greater (more negative) than $-1g$ you will find yourself standing on the roof of the elevator so it is now the roof that exerts a net downwards force on you. If the downward acceleration of the elevator is $-1g$ then the force on you decreases to zero and you become weightless i.e. ![]() If the elevator is accelerating downwards, for example $-0.5g$, the force exerted on you by the floor of the elevator is decreased and your total acceleration is decreased (in this case to $+0.5g$). In a stationary elevator it is the floor of the accelerator that exerts an upwards force on you, and this force is just $mg$ giving you an acceleration of $g$. ![]() When we say you are experiencing an acceleration this means something must be exerting a force on you, because force and acceleration are related by Newton's second law. Or am I misreading this? Does this person actually mean if the elevator is somehow accelerating downwards at 1.5 times the acceleration of gravity? In that case, I don't see how this would make any sense. So this is still just like the scenario when the elevator is accelerating upwards! But the reaction force therefore is downwards. Because when in an elevator, accelerating downwards at theoretically $4.9m/s^2$, the force normal will still be upwards (as it's preventing free fall), but will be less than if there was no acceleration (less weight). So I understand that the case scenario when an elevator is accelerating upwards, the net force on the person is in the up (positive) direction so the force applied by the person in reaction is in the down (negative) direction, which is positive g-force.īut I don't at all understand how you will feel an upwards force of -0.5g when an elevator is accelerating downwards. That's what a negative g-force is, when it feels like you are falling up. And if the elevator was acceleratingĭownwards very quickly, you might actually feel an upwards force of If you were in an elevator accelerating upwards which, you mightĮxperience a force of +2g.
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