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![[Post New]](/templates/default/images/icon_minipost_new.gif) 8 May 2007 11:58:15 IST
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a ball is projected vertically upwards with a velocity (gR)1/2 , R is radius of earth. to what height will ball rise?
a)R
b)R/2
c)R/4
d)3R/4
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Impossible is Nothing |
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8 May 2007 12:00:18 IST
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is it R/2 ????
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nupur.. |
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8 May 2007 12:15:18 IST
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Hi rpy I think the ans is a)R SOLUTION by ENERGY CONSERVATION TEi=TEf ---> PEi+KEi=PEf -GmMe/R+1/2mv^2=-GmMe/(R+h) where Me=mass of earth and h=ht reached g=Gme/R^2 -gR+1/2gR=-gR^2/(R+h) (since at heighest pt vel becomes zero) =>h=R answer
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8 May 2007 12:17:45 IST
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what's the answer????????
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"Imagination is more important than knowledge."
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8 May 2007 12:22:21 IST
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akku is rite: n priyesh when u conserve energy u shd take into account the gravitational energy between the earth and the mass m coz we consider THE EARTH'S MASS TO BE CONCENTRATED AT ITS CENTRE OF MASS and now the mass m is situated at a distance of R frm the earth so akku's answer is justified
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THERE'S SOMETHING BEYOND THE SKY
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8 May 2007 12:27:49 IST
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Thanks for_success for correcting my mistake.I've edited my post
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"Imagination is more important than knowledge."
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8 May 2007 12:28:51 IST
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Final vel = 0 (v)
initial vel = u = (gR)1/2
height= h
v^2 = u^2 --2gh (u and g are opposite)
or, h = u^2 / 2g = gR / 2g = R /2
option b is correct
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it is not important where u stand, but in which direction u are moving |
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8 May 2007 19:48:57 IST
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yes thats the correct ans akku..
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Impossible is Nothing |
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9 May 2007 00:27:14 IST
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Yeah, the answer is R. BTW, ramyani, the method that you've adopted to calculate the answer is totally wrong. You cannot use the equations of motion here as the acceleration due to gravity does not prevail during the entire motion of the body.
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Will nip in at times to solve problems :)
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9 May 2007 04:35:28 IST
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Answeris R. Methods are right.
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9 May 2007 05:11:41 IST
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simple question .............equate the energy,,,,,,,,,,,,ans is (a)R
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9 May 2007 09:57:42 IST
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thanks to all.i now got it right
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it is not important where u stand, but in which direction u are moving |
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