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We have studied that g (gravity)=9.8 m/s2..How did we get that value ?
asked Nov 23, 2015 in Physics by techdoubt (307 points) | 616 views

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According to Newton's Law of Gravity

Fearth=(GMm/d2) where 

M =  Mass of Earth

G = Gravitational Constant = 6.674×10−11 N⋅m2/kg2

m = mass of other object

d = distance between the object's center and the earth's center

Now we can re-write 

m.g = (GMm/d2)  OR          g = GM/d2

At Earth's surface d = radius of Earth =  6.371 x 106 m

Now in equation g = GM/d2

Put G = 6.674×10−11 N⋅m2kg-2

M = 5.972×1024 kg

d = 6.371 x 106 m

all we get is gravitational force g = 9.81 m/s2

 

answered Dec 6, 2015 by Arka (109 points)
selected Dec 6, 2015 by techdoubt
bingo!...good explanation !