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Mechanics

Blazing goIITian

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22 Feb 2007 13:07:30 IST

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plz reply

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The value of g will be 1% of its value at the surface of earth at a height of ( Radius of earth= 6400km)

a. 6400km b. 57600km

c. 2560km d. 64000km

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Comments (8)

Hari haran

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22 Feb 2007 13:35:56 IST

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Answer must be (c)

Prakriteesh Sarma

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22 Feb 2007 14:24:19 IST

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No, the answer is (b). Using the exact formula of variation with height h, we have, g = g₀(1+h/R)^-2

Now we know, g = 1% of g₀

So, g₀/100 = g₀(1+h/R)^-2

or,(1+h/R)²= 10²

or, 1+h/R = 10

So, h= 9R = 9 X 6400 km

= 57600 km

Himanshu

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22 Feb 2007 14:30:17 IST

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IS ANS (B)

swagato chatterjee

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22 Feb 2007 14:57:26 IST

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g = GM / R²SO , from this eqs. we can say that g

1/R² or , g1/g2 =( R_{2 /}/ R₁)²
OR, g/ (g/100) = (R2 / 6400)²
OR, R2²= 6400². 100 g/g = (6400)^2. 100
OR, R2 =6400 .10 = 64000

SO THE ANS. IS 64000 KM. (d)
send rply if correct

avdesh100

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22 Feb 2007 15:27:05 IST

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the answerr is B)

sss tolay

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22 Feb 2007 15:28:56 IST

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hey ron,u have done rt. but height is asked i.e. distance from the surface of the earth.you have calculated the distance from the centre of the earth.so, the answer is b).

vasanth_mech pilani

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22 Feb 2007 16:40:54 IST

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g₀/100 = g₀(1+h/R)^-2

(1+h/R)²= 10²

1+h/R = 10

h= 9R=57600 km

answer is b)

the distance is too far from the earth...... so h can not b neglected with respect to R..... so u cannot use the binomial theorem in the expression g(1+h/R)^-2

cheeeeeers....

Nupur Goel

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22 Feb 2007 19:20:14 IST

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yups!! the ans is B..thanx guys...

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