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General Category => Maths, Geometry, Physics and others => Topic started by: que_base on September 01, 2008, 01:03:27 AM

Title: freefall
Post by: que_base on September 01, 2008, 01:03:27 AM
Can someone explain me IN SIMPLE WORDS how can in free fall, something that weights 1 kilo and something that weights 1tone to fall with same speed ?  :-\ :-\ I just do not get it
Title: Re: freefall
Post by: kam on September 01, 2008, 18:30:25 PM
I know what you mean.

The thing is that in free fall as you mean it, the objects fall only under the effect of gravity. This means that there is no other force on the items like air drag or anything else. This must be true in order to have:

Acceleration of gravity here on earth is 9,83m/sec2, usually we say 10m/sec2. This means that, the acceleration of every object, no matter what size or shape, will be 9,83m/sec2 and is signed with the letter 'g'

Proof:
In respect tot he Newtons 2nd law:
Ftotal= m * a
The total force applied to an object during fall, is the mass of the object m multiplied to the acceleration of the object a. The ONLY force applied is the weight of this object (W).

Because F=W (NO OTHER FORCE APPLIED) :

a=Ftotal/m =W/m = (m*g)/m

I this point, m will go away (m/m=1) so

a=g

This means that the acceleration of object is g, no matter the weight.
Title: Re: freefall
Post by: Supernova on September 02, 2008, 17:50:38 PM
You can make an experiment with a heavy sphere and a smaller sphere. They should be made of iron. One should weight like some 200-300 grams and the other like 2-3 kilos or more.
Choose spheres because they will have less air drag to any other shape.

Throw them from a tall building like 4-5 flats height.
You will notice that the difference is extremely small. They will almost fall the same time. Almost, because the air drag will cause a slight friction to the bigger sphere.
Title: Re: freefall
Post by: kam on September 02, 2008, 21:09:42 PM
Yes, and thinking of it, it is most possible that the light ball will fall faster than the heavy ball... I mut check this out  ;D

I will make an experiment from my house, the 4th floor. From one side is like 15meters height. Wait for the results...
Title: Re: freefall
Post by: spic0m on September 02, 2008, 21:11:25 PM
Beware of any pedestrians!  :)
Title: Re: freefall
Post by: que_base on September 02, 2008, 22:48:27 PM
Well, it gets better. I am not sure if i own it...
But i will study more your answer and hey, kam, i wait the results from yous experiment  ;)
Title: Re: freefall
Post by: spic0m on September 02, 2008, 22:54:05 PM
Maybe he's at the police station allready, i told him to be carefull!