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JEE Main 202331 JanuaryEvening Shift
Exam
JEE Main
Year
2023
Date
31 January
Shift
Evening Shift
Subject
Physics
Chapter
Gravitation

JEE Main 2023 · 31 January · Evening Shift · Physics · Gravitation

A body weight W , is projected vertically upwards from earth's...

A body weight WW, is projected vertically upwards from earth's surface to reach a height above the earth which is equal to nine times the radius of earth. The weight of the body at that height will be:A body weight W , is projected vertically upwards from earth's surface to reach a height above the earth which is equal

Options

  1. AW91\dfrac{W}{91}
  2. BW100\dfrac{W}{100}
  3. CW9\dfrac{W}{9}
  4. DW3\dfrac{W}{3}

Correct answer

B. W100\dfrac{W}{100}

Step-by-step solution

A body weight W , is projected vertically upwards from earth's surface to reach a height above the earth which is equal

Final distance from the centre of earth wil be R+9R=10RR + 9R = 10R.

Now acceleration due to gravity at any height(distance from centre r) is given by,

g=GMr2g = \dfrac{GM}{{r}^{2}}.

Therefore,

g′=GM(10R)2{g}^{'} = \dfrac{GM}{{\left(10R\right)}^{2}}

Now, value of gg at surface will be, GMR2\dfrac{GM}{{R}^{2}}.

Hence,

g′=(g100){g}^{'} = \left(\dfrac{g}{100}\right).

Then, W′=mg′=mg100=W100{W}^{'} = m{g}^{'} = \dfrac{mg}{100} = \dfrac{W}{100}

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