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What if I could show you the answer? :P
https://www.youtube.com/watch?v=iuUghXPLeuw I performed this quite a while ago.. take a look
wait but why does weight decrease
Your weight, is determined by how much force the ground puts on you (we call that as the normal force) If the elevator is accelerating downwards, then, you can sort of imagine that the floor is 'TRYING' to move away from you. Which means less force on you? or less weight? Does that give you some sort of intuition?
when you are going down, the net force is going down so aren't you suppose to be heavier
there is a greater force acting down
It is true that there is a net force downwards.. But that doesn't decide your weight. Think another way.. when you move in a bus, if the bus accelerates forward, you feel an 'inertial push' backwards? Similarly when the bus brakes, or when bus takes sudden left turn, you feel an inertial push forward, or rightwards? Thus you always feel some kind of push in the opposite direction of the acceleration. So when your elevator is accelerating downwards, you will "feel" an inertial push upwards, reduces your weight. make sense?
but if there inertia is pushing you up, there must also be another force besides gravity pushing you down???
why? why would you say so?
and it is not 'inertia pushing you up' it is, 'an inertial push'.. that is not really a force, it just FEELS that way
normal force is less than mg there for mg( your weight) is heavier....
mg is NOT your weight. mg = the gravitational force your weight = Normal force.. now most textbooks say mg is your TRUE weight, and the normal force tells you your APPARENT weight.. but I don't like that definition.. I just say whatever is the normal force on you.. that is your weight!
mg is gravitational force which depends on your weight
normal force is force exerted by the elevator floor
Let me use some numbers say your mass is 50kg, and g = 10 Then mg= 500N say your elevator is accelerating down at 5 m/s^2 then Normal force is 250N. (i am sure you can arrive at those numbers) Now.. read carefully Since the floor of the elevator is pushing you up with 250N of force, You my friend is also pushing DOWN on the floor with 250 N of force agree? So if you put a scale underneath you.. that scale would register a 250N of force. and hence it would give you a reading of 25kg..
What part didn't you get?
why you are lighter if mg is greater
I just told you.. Your mg is always the same (on surface of the earth at least) But that doesn't tell you much about your 'weight' or what you 'feel' What you feel as weight is due to the fact that the ground is pushing you up. you cannot just 'feel' forces. This is actually quite subtle.. :P
so if you are feeling something then aren't you feeling more weight
That depends on which direction you are feeling.. :P
yea.. but in this case you are 'feeling a push up' remember you always 'feel' in the opposite direction of the acceleration